I was thinking of buying a Glock and then...


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atblis
January 16, 2006, 05:10 PM
http://filebox.vt.edu/users/atblis/DSC00363.JPG
http://filebox.vt.edu/users/atblis/DSC00356.JPG
http://filebox.vt.edu/users/atblis/DSC00366.JPG

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Manedwolf
January 16, 2006, 05:13 PM
Dude! Reduce your picture size!!!

dasmi
January 16, 2006, 05:17 PM
Learn how to resize your pictures, everyone. This is getting insane.

middy
January 16, 2006, 05:29 PM
Yeah, because no other handgun has partial chamber support... :rolleyes:

ABBOBERG
January 16, 2006, 06:39 PM
Atblis: Could you try a lower screen resolution? I can't even see the whole image.

As far as partial chamber support - what does that mean? The chamber support in my Kahr PM9 is at .165" from the breech face. The "solid" area inside my 9mm ammo was about the same number, so does that mean the Kahr has "zero" support? If the feed ramp goes back to, say .185", does that mean .020" of "negative support"? What support do the Glocks normally have, in say, 9mm?

KingB
January 16, 2006, 07:50 PM
This is what middy is talking about.

atblis
January 16, 2006, 09:12 PM
every other 10mm I've ever fired doesn't do that (Even pushing a 180gr at 1380 out of a 4.25" barrel).

Rexrider
January 16, 2006, 09:33 PM
atblis

Alright. I see pictures of a 10mm casing with a hole in it. I hole that is typical of an unsupported chamber. But that is all I see.

What is the rest of the story? Assuming the casing was fired from a Glock, what is the story on the ammo? Was it new factory ammo or reloads?

What happened to the handgun? Was there damage? Was it an actual Kaboom?

If you are going to post pictures like that please include the facts that go with the pictures.

You are welcome to make whatever choices you wish. Even if that includes not buying Glocks based on that one casing. But for me I have been very happy with the Glocks I have owned over the years and will continue to own them.

HSMITH
January 16, 2006, 09:34 PM
Ever hear of setback? 10mm isn't immune, and I think you will find that the case support is pretty close to a 1911 type in the Glocks.

It could have been slightly out of battery too.

lee n. field
January 16, 2006, 09:47 PM
Assuming the casing was fired from a Glock,

The rectangular impression from the firing pin strike -- If the second picture was of the same caseing, it was.

wally
January 16, 2006, 09:53 PM
Learn how to resize your pictures, everyone. This is getting insane.

Cropping so we see the brass at high resolution and don't see the table top is what needs to be done. Simply resizing will not show the detail he wants it the brass because of all the pixels used for the table top.

If you don't have a photo editor software, you can download the GIMP (Gnu Image Manipulation Program) for free www.gimp.org Its available for most popular systems and almost as good as Adobe Photoshop.

--wally.

FPrice
January 16, 2006, 10:05 PM
Thge following is why I sold my Glock 23 and will not buy another .40 Glock. But in all fairness, this was early Federal brass and was not as strong as the current brass.

http://i9.photobucket.com/albums/a56/FPrice/G23Shell.jpg

Rexrider
January 17, 2006, 12:36 AM
The rectangular impression from the firing pin strike -- If the second picture was of the same caseing, it was.

Yes, your right, my bad.

I can't even use the excuse that the picture was too small to see it clearly :D

atblis
January 17, 2006, 12:41 AM
Those were new factory rounds. The brass is now worthless though.
There wasn't a hole in the brass. It was just bulged really badly. I've never been able to duplicate that with the Witness with anything I've managed to cram in there. That was the worst bulge I've ever seen. Every case did that. Not just one (so I think we can rule out setback).

The 17 is a fantastic pistol. You just need to get another barrel for the 20. Spending $500+ on a pistol and then needing to get an aftermarket barrel to make it safe is kinda pathetic.

I was thinking about getting a 20, but having to get another barrel bothers me.

atblis
January 17, 2006, 12:52 AM
Yes it was Glock.
No they were not reloads.
Glocks have some issues (perfection my ass).

Texshooter
January 17, 2006, 01:13 AM
Glocks indeed have some issues. Not the least of which is being honest with their customers.

As stated above, "perfection my ass."

MTMilitiaman
January 17, 2006, 01:25 AM
That's funny. My 20 has never done that. I am shooting Double Tap almost exclussively. That's a 180 gr FMJ @ 1250 fps. The 180 gr GDHP @ 1300 look pretty much the same. Nothing to sneeze at. Tell Mike McNett you need another barrel for the Glock 20. It is my understanding that he has fired thousands of rounds for testing and development of his ammunition through a stock Glock 20. There is absolutely nothing wrong with the standard Glock barrels unless you want to try handloading the 10mm into something atomic--and then a good argument could be made that the problem is again with the ammunition. The 10mm Auto is perfectly capable on its own without you trying to turn it into something it isn't. If you feel the need to replace the standard Glock barrel with something that offers more support, by all means, go for it. You still have a nice polymer framed 10mm Auto with less cost than an HK or SIG in a lesser cartridge. But don't go around thinking that you need a new barrel. No sir, you only want a new barrel because of percieved deficencies in the standard barrel.

Glock may have issues--with all that reliability, and that damn Tennifer making it so durable and corrosion resistant. And the things are so simple, and all that magazine capacity. Geez. I wonder why the things are so popular since they suck so much :uhoh: :scrutiny: :rolleyes:

But lets please leave your ass out of this :neener:

MachIVshooter
January 17, 2006, 01:29 AM
Yeah, because no other handgun has partial chamber support... :rolleyes:

Your point would be valid if we were talking about .45 ACP, but 10mm is a whole different animal. Kimber, S&W, Dan Wesson, Tanfoglio all use fully supported chambers in their 10mm models.

I own a Kimber, S&W 1006 and Witness Compact 10mm and none of them have ever ejected a case that looked like that (FWIW, my loads run 180 grain pills at 1406 FPS from the 5" guns and 1342 from the Witness' 3.5" tube). I use all makes of brass with my loads and none have ever exhibited such failure. This is a Glock problem.

On a similar note, I have found that reloading brass fired from a Glock does not work well in other pistols. The Glock's chamber design and sloppy tolerance causes excessive case head expansion past the furthest reach of the resizing die. I got rid of my Glock 22 some time ago in favor of a S&W 4006.

MTMilitiaman
January 17, 2006, 01:59 AM
Those manufactures probably put full case support on their .45 barrels too. The Glock chamber specs are still within SAAMI limitations. And they are cut loose to increase reliability. It is only a problem for people simple enough to be pursuaded by Internet gossip. The Glock is probably one of, if not the more durable 10mms on the market, and is almost without a doubt among the most reliable pistols of any caliber that you can buy at any price. But if it means that much to you, get an aftermarket barrel for it. Even with the new barrel it will still run you less than most of those other brands.

atblis
January 17, 2006, 02:30 AM
Where would you find that? On a message board? Nahhh

The pictures really dont do the case justice. It looks much worse in person. I like to reload. IMO that brass is toast. What would a touch of setback do? Can anybody say Kaboom?

Grayrider
January 17, 2006, 11:17 AM
Atblis,

I am glad you posted this as I sold my G20 recently. No regrets now after seeing your pics. My Witness Match in 10mm took its place. I am still tempted by a polymer 10mm though. Maybe I should drop some cash on a Witness P series and just see how they run.

:D

GR

000Buck
January 17, 2006, 02:26 PM
I think maybe there is something wrong with either that ammo, the brass, or your gun, like someone else said, possibly firing slightly out of battery? I have a G20 and G29 with stock barrels, and have ran lots of super hot, in fact, well past published data for BlueDot and Power Pistol loads, and have never seen anything like that.

I also have a Witness and 1006 in 10mm, both a nice guns, but the Witness isnt as reliable as the G20/G29, and the 1006 is much lower capacity and has a horrible grip to me. There are lots of G20s out there that fire alot of hot rounds with no problems, so I think there is something else going on here.

EDIT: All makes put out a few lemons, everyone seems to love the 10mm Witness, but mine is unreliable, so I wouldnt recommend one of those.

MTMilitiaman
January 17, 2006, 02:35 PM
Atblis,

I am glad you posted this as I sold my G20 recently. No regrets now after seeing your pics. My Witness Match in 10mm took its place. I am still tempted by a polymer 10mm though. Maybe I should drop some cash on a Witness P series and just see how they run.

:D

GR

Whatever :rolleyes:

If you guys are so simple as to be that easily pursuaded to abandon an entire design because of a single incident, then you deserve to be cheated out of fantastic handguns. We don't even have the full details and I already showed examples to prove that not only does this not happen with all Glock 20s, but indeed, it is rather rare. I say it is rather sad, pathetic actually that people can be this gullable and this jaded towards a design. But whatever. Your loss.

1911Tuner
January 17, 2006, 02:52 PM
Anybody wanna hear the real explanation on what caused this? Ah'm yuh Huckleberry! Anybody who may be annoyed, please skip the following comments...:p

No denying that Glocks have less than ideal head support at the bottom of the chamber. All it takes is a quick peek to see it. There are also several 1911-pattern pistols that have been subject to over-zealous barrel ramping/throating that have even less case head support in that area.
Some bulge case heads and some don't...just like the Glocks.

Why do some bulge or even blow case heads while others don't? Well, ammo plays a role in the occurrence. Some brass has a thicker area just forward of the web than others. Those will withstand higher pressures without bulging...or at least not bulging to this level. Federal will bulge more readily
than PMC or Winchester. Not a cheap shot at Federal...just a fact.

Some cases are tougher than others, but that in itself isn't the determining factor, nor is the reduced head support common to Glock and other designs.
Headspace is...or rather, excessive headspace that is excessive in the wrong direction. (See the sticky at the top of the gunsmithing page for an explanation)

When headspace is excessive...or even close to maximum in the wrong direction, two critical things occur when the gun is fired. First, and most critical is that the breech opens partially as the slide is slammed rearward under pressure, while the barrel is nailed full forward. If headspace is excessive, a gap opens between barrel and slide. It's not much of a gap...but it's sometimes enough to cause the case head to become dangerously unsupported.

The next thing that happens is that the case...under full chamber pressure and not having the slide's solid support at the rear...backs out of the chamber until it contacts the slide again, and stops. If the combination of undercut barrel throat and excessive headspace is such that the thin section ahead of the web becomes completely unsupported, you have a bulge. In worst-case scenarios...and/or with thin brass...you have a case failure, aka blowout, aka ka-boom.

A case failure at the head isn't the real danger in modern semi-auto pistols.
Most take it in stride, sometimes with the occasional bulged magazine. The dangerous part comes when the hot gasses and shards of brass vent into the magazine and cause sympathetic detonation of more rounds withing the confines of the magazine and grip frame. Fingers and eyes can literally be lost to the ages.

If you experience bulged cases, have somebody check the headspace before proceeding.

Cheers!

atblis
January 17, 2006, 03:48 PM
I would guess that DT uses Starline. Though the lettering looks like Hornady (WHo makes Hornady's brass anyways?).

JohnKSa
January 18, 2006, 12:07 AM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

How old and what weight was the recoil spring in the gun that fired that case?

jeepmor
January 18, 2006, 12:44 AM
tuner said it all.

Hope you can get it repaired. I would not condemn the Glock product line entirely, but I would question their quality control. Aren't those german guns? I thought Germans made the best stuff in the world. That's what all the germans I know tell me....they all drive Toyotas though..hmmmmm.

jeepmor

atblis
January 18, 2006, 12:53 AM
but this is too amusing so I'll let this go on for a while.

Again I will reiterate that I have pushed 3 different Witnesses harder than factory double tap loads, and absolutely none have had brass that looks like that come out of the chamber.

Additionally, there's no way DT is using crappy brass (at least I hope not).

JohnKSa
January 18, 2006, 01:21 AM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

Sure, take your time. We exist merely for your amusement.

Do you know the condition/weight of the recoil spring, or is withholding that information amusing as well?

tlend
January 18, 2006, 02:06 AM
tuner said it all.

Hope you can get it repaired. I would not condemn the Glock product line entirely, but I would question their quality control. Aren't those german guns? I thought Germans made the best stuff in the world. That's what all the germans I know tell me....they all drive Toyotas though..hmmmmm.

jeepmor


I believe they're Austrian (but same same right? :) ) Anyway, I know the topic's pretty much been hammered to death but I gotta say, I own two glock pistols, and have at least 5000 rounds through each. Neither has been modified, repaired, or had anything other than cleaning (by my hands). I have never had a swollen case head/ammuntion malfunction that i would consider a critical malfunction. To each his own.

ny32182
January 18, 2006, 02:15 AM
A G20 will probably be my next pistol, but the first time I see a case that looks like that come out of it, I'm springing for an aftermarket barrel. There are entirely too many reports of KBs with G20s for it to be anything other than a problem with the factory barrel. I don't care what their excuse is; it is something that *should* be fixed. My personal theory is that their ramp design and chamber dimensions are close enough to a dangerous lack of support that a few barrels on the outside edges of their tolerance escape the factory in a truly dangerous state. Not that Glock would ever admit it.

My Double Tap ammo is actually marked with the Starline symbol on the brass, so unless they have switched suppliers, it is probably Starline.

Grayrider
January 18, 2006, 11:08 AM
Yet again Tuner teaches me something I did not know. Good information for those that are willing to listen.

;)

Seems like a barrel would be wise for anyone wanting to run the warmer 10mm from a G20. I have owned three of them and found that they showed more signs of pressure from hotter loads in the fired brass than I had from a Witness or S&W 10mm. I had some really hot ammo that the Smith ate fine, but the G20s completely choked on. I recently ran the rest through my Witness Match without any problems. Of course none of the Glocks gave me issues with the more mundane 10mm loadings out there.

GR

atblis
January 18, 2006, 12:02 PM
perhaps caused by a worn out recoil spring, aggravated by the loose chamber and feedramp issues that everyone is aware of (but some pretend don't exist).

Not all Glocks do it, but it appears to be enough of an issue that....

They probably still use Starline. They just started using their own headstamp.

Don't get pissy guys. I never said it was my pistol.

With wussy factory loads the Glock doesn't appear to have any problems. With 10mm loads on the warmer side... Maybe I'll buy one over the summer and see if I can get it to kaboom.

New Glocks 20 $550
After market barrel $180
Not having your piece of plastic perfection explode in your face, Priceless.

I do like Glocks. It's just the prospect of having to buy a new barrel that keeps me from picking one up.

1911Tuner
January 18, 2006, 12:29 PM
atblis said:

>perhaps caused by a worn out recoil spring,<
***************************

Nope. The Glock is recoil-operated, and the recoil spring has very little, if anything to do with it. Don't know the specifics on the Glock when it begins to unlock, but by the time it starts to unlock and open the breech, the bullet must be gone. Since the start of unlocking with a short-recoil system occurs at very little slide travel distance, the recoil spring compresses very little. In a 1911, this event comes with about a tenth of an inch of slide travel, so you can understand that the difference between spring loading in full battery and
that little bit of travel would be negligible to the point of zero effect.

OTOH, if the gun unlocks too early, while the bullet is still present and pressures are high, it could very well be why the case bulged or blew...
but this is a mechanical timing event not affected by the recoil spring.
There would be evidence of early unlock at the front corner of the barrel locking lug. Radiusing, setback, or a general rounding-off of the corner
that occurs because the barrel is being pulled down while the barrel and slide lug are nailed together under pressure. To better understand, the breech locks up under presure, when it's fired...not when it's simply in battery.

ny32182
January 18, 2006, 01:28 PM
The way I see it, it is the only 15+1 10mm out there at $550, or even at $750 if you end up needing a new barrel. The capacity is what makes it worth a look for me.

atblis
January 18, 2006, 01:51 PM
I also don't believe the recoil spring has much to do with the lockup (That's why I run stock springs). I always like to ask people what they think will happen if you fire a pistol with no recoil spring. Is it going to blowup? I don't believe a 22lb+ spring buys you anything except broken slide stops.

What I meant is that the recoil spring was to weak to make it go fully into battery (didn't feed the next round correctly).

How about 15 +1, no new barrel needed, and about $300 dollars? Every heard of the Witness? Really a nice pistol. EAA has done just about everything they can to get people to not buy them.

000Buck
January 18, 2006, 03:53 PM
I have Witness compact, it is a nice pistol, but mine is unreliable with hot ammo, well, actually what the standard ammo was. What would you recommend I try to fix it, a stronger recoil spring or magazine spring? It stovepipes once in a while, which is the opposite of what I would think it would do with hot ammo.

I also don't believe the recoil spring has much to do with the lockup (That's why I run stock springs). I always like to ask people what they think will happen if you fire a pistol with no recoil spring. Is it going to blowup? I don't believe a 22lb+ spring buys you anything except broken slide stops.

What I meant is that the recoil spring was to weak to make it go fully into battery (didn't feed the next round correctly).

How about 15 +1, no new barrel needed, and about $300 dollars? Every heard of the Witness? Really a nice pistol. EAA has done just about everything they can to get people to not buy them.

atblis
January 18, 2006, 06:11 PM
I am talking about the Full Size steel guns. I've never liked the compacts or the polymer guns. The fullsize steel guns are decent guns.

JohnKSa
January 19, 2006, 12:40 AM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

by the time it starts to unlock and open the breech, the bullet must be gone.That's the way it's supposed to work. The combination of the slide/barrel weight and the force of the spring allow one to calculate a time constant that indicates how fast the system will respond to the firing impulse. Mechanical engineering has equations for performing the calculation. If the spring is too weak, the time constant can be small enough to allow early opening. Sometime ago, someone (I believe it was MarkCo) did some experimentation and posted the results. He was experimenting with a .40 cal Glock and was able to eliminate the case bulges by using heavier recoil springs. Just as the mechanical theory suggests.mechanical timing event not affected by the recoil springNope, the spring plays an integral part in the timing. If you poke me hard enough ;) I'll dig out my control theory book and post the equations. If I'm lucky, some college engineering student will know them off the top of his head and save me the work. :Dthe difference between spring loading in full battery and that little bit of travel would be negligibleYes, that is correct, however the force that the spring is applying while the gun is in battery (it's still under significant compression at that point--as demonstrated by what happens when you let go of one early during disassembly :eek: ) is not negligible and makes a big difference in how fast the gun unlocks/opens.

jungle
January 19, 2006, 12:59 AM
I have to agree with Tuner for the most part. The mass of the recoiling parts and geometry of the barrel cam have far more effect than the recoil spring on unlock speed.
Most Kabooms in guns with proper headspace have been traced to bad ammo.
Glocks in .40 S&W have been known to be too generous in the ramp/chamber interface. Early .40 brass was thinner in the web area. That said, there is something very wrong with either the ammo or pistol in question and I have not seen a Glock with a headspace problem.
In a properly fit and ramped barrel even a little excess headspace is seldom a problem and forward movement of the case is halted by the extractor. This is why you can fire a .380 in a 9mm without ill effect. As pressure goes up, all of these factors become more critical. 35,000+ PSI will amplify any errors in brass or pistol.

JohnKSa
January 19, 2006, 01:43 AM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

I always like to ask people what they think will happen if you fire a pistol with no recoil spring.If you ask, you should know the answer. What happens? No guessing, let's see the theory put into practice. ;)The mass of the recoiling parts and geometry of the barrel cam have far more effect than the recoil spring on unlock speed.IIRC, the time constant is linearly related to both the mass and the spring force--they both contribute equally. However, that doesn't mean that the PRACTICAL contribution is equal since the practical contribution has to do with the actual measured mass and spring force which may not be similar in magnitude after the proper unit conversions have been made.

albanian
January 19, 2006, 01:50 AM
"Aren't those german guns? I thought Germans made the best stuff in the world. That's what all the germans I know tell me....they all drive Toyotas though..hmmmmm."

LMFAO!:D

albanian
January 19, 2006, 01:52 AM
Glock Perfection?

Correct me if I am wrong but wasn't it an Austrian that came up with the original "Big Lie"? Now we seem to have another Austrian telling us another "Big Lie". Fool me once shame on you...:neener:

jungle
January 19, 2006, 01:58 AM
A 1911 will fire and eject just fine without a recoil spring.

In the very short distance the slide and barrel travel to unlock the recoil spring in effect contributes to the force required, if you want to know how much just measure the force required to compress that particular spring 1/10th of an inch.

Mass is required to handle the momentum, otherwise we could just build slides out of plastic with steel breechfaces and get stronger springs. Not going to happen.

The recoil spring serves primarily to slow slide velocity at the end of the recoil stroke and to return the piece to battery.

JohnKSa
January 19, 2006, 02:09 AM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.we could just build slides out of plastic with steel breechfaces and get stronger springsThat's true--except the springs would have to be much stronger than you expect. A person has to be able to manually operate the slide--that puts an upper limit on how strong the spring (and therefore how light the slide) can be.measure the force required to compress that particular spring 1/10th of an inchIt's not how much the spring is COMPRESSED by the slide movement, it's how much FORCE it's exerting to hold the slide closed when the gun is in battery. The former is negligible, as noted already, the latter is significant. Remember, the spring is already significantly compressed when the gun is in battery--therefore it's already exerting force to hold the gun in battery before the slide begins to compress it due to the firing impulse.A 1911 will fire and eject just fine without a recoil spring.That might be true, although I think one would experience some problems fairly quickly. But that's a 1911--we're not talking about 1911s. While a hammer driven gun still has spring force (hammer spring) holding the slide closed even without a recoil spring in place, a striker gun like the Glock does not. There are at least some on this thread that KNOW that the hammer/hammer spring force is a significant effect in the 1911. That's not present in a Glock--the only significant forces resisting slide/barrel motion in the Glock are the mass of the slide/barrel combination and the force of the recoil spring.

jungle
January 19, 2006, 02:17 AM
Agreed, in the Glock the striker spring contributes to opening force and with a weak recoil spring just pulling the trigger may cause the slide to move rearward.
Although the striker spring's effect is cancelled as the striker is released.
When I said measure the force required to compress the recoil spring for the first 1/10th of an inch, I meant as it lies in battery. It is the weakest force in that springs movement. Just as in an exposed hammer design, the hammer spring has it's lowest force applied in the first fraction of an inch of slide movement.

JohnKSa
January 19, 2006, 02:26 AM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

jungle,

It's not about compressing the recoil spring--that figures into it, but as you point out, that's not a significant contributor. The significant contribution of the recoil spring is the amount of force it's applying to HOLD the gun in battery even before the slide starts moving.

The spring is ALREADY compressed when it's installed in the gun, even when the gun is in battery. That's not apparent in the Glock with the captive spring setup, but it's obvious in a setup with a free recoil spring. For example, the recoil spring in my P89 is about 13 cm uncompressed. When installed in the gun, it is compressed to about 8.5 cm. That means that even when the gun is in battery, the spring is ALREADY compressed by about 35%. It is definitely applying significant pressure to keep the slide forward.

jungle
January 19, 2006, 02:31 AM
Understood, the recoil spring is applying force in battery on both designs. Now measure the total force required to move that compressed spring that fraction and that is it's total effect on the unlock cycle. Period.

bevis
January 19, 2006, 04:53 AM
ya know, im not a glock hater or lover. they are good guns that
i just dont like all that much. they are very reliable and we all
know about their finish. but really, buying a new weapon and
then spending another $150 on a barrel for it. dont seem to
cost effective to me. it seems that more often than not, when
a kaboom is mentioned in a thread, the word glock is in the same
sentence. so why do glock fanatics continue to proclaim that
kabooms are mostly blamed on reloads when this is obviously
not the case ? i traded off my G23 that i never had a problem with but the unsupported chamber thing was always in the back of my mind. im not slamming glocks . im just curious as to why glock fanatics cant see
that there is somewhat of a real world problem with kabooms with
factory ammo. which to me would be cause for concern.

jungle
January 19, 2006, 05:02 AM
If the kaboom issue in .40 cal. glocks was real problem I think the FBI, and the many state, federal and local agencies using them would have dropped the gun and or caliber. Federal did have to recall some lots of ammo.
I think most real world users have been pleased.

The fact is that all sorts of pistols and rifles blow up, and it usually has more to do with the user and the ammo than the weapon.

1911Tuner
January 19, 2006, 09:22 AM
John...Looks like we ARE gonna do it again...:p (Gunny Tuner slaps JohnK on both cheeks with the ceremonial white gloves.):D

Some years ago, a talented pistolsmith named Ned Christiansen repeatedly fired a 1911 pistol without a recoil spring...without ill effects. He used a shock buffer on a full-length guide rod to prevent excessive frame damage, and the gun functioned as if it didn't know the difference...other than the brass flyin' into the next county. The unlock timing didn't change to any practical degree.

The recoil spring's 1/10th inch of compression is negligible in its effect...and the in-battery preload doesn't have a whole lot more at about 3.5-4 pounds, depending on the load rating of the spring. While a seriously tired spring may allow the gun to fire slightly out of battery, that's basically a spec problem.

Early unlock does occur, but its effects on the locking lug or lugs are pretty readily apparent if pressure is high enough to cause a case bulge or blowout. Remember how the tilting barrel design functions. The barrel would have to drop out of engagement with the slide while the lugs are still being forced together under full pressure. The compression forces would be on the order of 15,000 psi in a .40 or a 9mm...assuming that the pressure had spiked and fallen off to about half of the peak figure at unlock. Use a hydraulic press to
compress a 1/2 square inch steel disc to 15,000 psi and try to yank it out from under the arbor to see what I mean.

You can contact Ned on various forums to get the finer details of his experiment. For now, I'm gonna do a best WAG and attribute this
particular case bulge to excessive headspace. If the owner has it gauged and reports back, we'll know. If he doesn't...all we can do is speculate.

John! When ya comin' to North Cackalackey? Coffee's on!:cool:

jungle
January 19, 2006, 11:32 AM
Headspace could do it, as could firing slightly out of battery(reduces lock up lug area and distance to unlock), but I'll go with ammo that is too hot-because that has been the direct cause in most of these incidents. My understanding is that it shoots other factory ammo without problem.

In any case I would stop shooting that ammo in that gun, because it has already warned you quite plainly that something is badly wrong and you might not get any more warning before something lets go.

To those who think that factory ammo is faultless, take a look at the recall lists from various companies one day.

atblis
January 19, 2006, 07:32 PM
Powder manufacturers let things slip from time to time.

jungle
January 19, 2006, 07:56 PM
atblis, Does this pistol run with Winchester or other brands without producing bulged cases?

..
January 19, 2006, 08:33 PM
It is only a problem for people simple enough to be pursuaded by Internet gossip.


Internet induced hysteria.

JohnKSa
January 19, 2006, 11:23 PM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

the brass flyin' into the next county. The unlock timing didn't change to any practical degree.The brass flying into the next county means faster slide velocity. Faster slide velocity means faster unlocking. Sure, the recoil spring would be doing some deceleration by that point, but it's also retarding the initial movement with the 3-4lbs of preload you mention (I think it's probably closer to 7lbs actually). How much retarding force is the inertia of the slide/barrel combo (weighing at most 2lbs) providing?

How did he measure the "no practical degree" of difference? By case bulge? Case bulge is ultimately the result of pressure--what's the pressure difference between .45ACP and 10mm? Wouldn't the pronounced pressure difference of the two rounds result in a pronounced difference in case bulge if both guns unlocked early by the same amount?

Also, you skirted the issue about the force dissipated by recocking the hammer although you've posted before how important that is. That force is not dissipated in a design like the Glock.

Testing in Glock pistols (this thread was about Glocks, right?) has shown that increasing the recoil spring weight has a noticeably positive effect in reducing case bulging in .40 S&W. I can't imagine why that wouldn't apply equally in the 10mm.

1911Tuner
January 19, 2006, 11:37 PM
John...The unlocking part is a mechanical event. It occurs when it occurs, regardless of the spring's load, or lack thereof. You can alter the slide's velocity with spring change...but not the unlock timing.

No practical degree of difference...meaning no damage...no bulged or blown cases, etc. You'll have to contact Ned to get the full story.

I've also heard that the problem seems to occur more with the .40 than with other calibers. Gotta believe that the unsupported area under the head and headspace that's right on the peg are the major contributors. Otherwise, we'd see it in almost all .40 Glocks...and likely 10mm too. Early unlock timing could also play a role...but i think that if the guns that produced bulged or blown cases were checked for headspace, that it would probably tell the story. Independent, uninterested party, of course.

Think about what causes case head separation in rifles firing virgin ammo. Excessive headspace. It'll cause bulged brass in straight-walled autopistol cases too. In every instance that I've seen it in 1911s with or without altered barrel ramps, headspace has been off the scale.
With a high-pressure round like the 40...and the unsupported area like the Glocks have...it wouldn't have to be that far out of spec.

No, the hammer resistance isn't there with the Glock. COmpensation may have been made by delaying the unlock sequence. Don't know what the starting point for the unlock timing is in the Glocks...but I'd be willing to bet that it's later than with the 1911. Glock armorers...any information on this?

jungle
January 19, 2006, 11:54 PM
John, There may be some merit to your argument. The problem is primarily one of momentum, which is why the bullet gains much more energy than the recoiling mass-F=MA and all that.
Consider for a moment though that the base of a .45 caliber bullet is .159 square inches and 20,000PSI is applied to it. That would yield a momentary force of over 3680 LBS. You can prevent the slide from most movement with your bare hand, but that initial acceleration and pressure curve is quite steep, the bullet has left the barrel in about .002 of a second.

I would enjoy seeing the data you have collected though and any calculations you used to arrive at your conclusions.

Tuner, I believe the Glock delays unlock a little longer, but that the unlock event is quicker, which is why their short barrel versions work a little better than the micro 1911s, no hard data but my impression after close examination of the locking surfaces and cam. As far as headspace in Glocks, that just doesn't seem to be a problem and it would lead to far more problems considering most of them use cartridges in the 30,000+PSI range. The 1911 has, as you know, more than double the headspace allowance of the higher pressure rounds which are usually at .01. Gunny, I always enjoy it when the white gloves come out.

jungle
January 20, 2006, 01:02 AM
Just one more point John, Browning tilting barrel designs do not unlock before the bullet exits and pressure drops to zero. Calculate MA for bullet and 20 ounces of recoiling mass alone and show the difference in movement-all without any springs.
The mass will take at least five times the time to move to the unlock point that the bullet takes to exit the barrel. Try it yourself and report back.

JohnKSa
January 20, 2006, 01:18 AM
jungle,

The testing I was referring to (in regard to case bulging & recoil springs) was something I saw posted on the web some time ago. I've been trying to locate it with no success.That would yield a momentary force of over 3680 LBS.That force is largely balanced while the bullet is in the barrel. The motion of the bullet prevents it from being completely balanced. Because it is largely balanced, the net effect on slide motion is much smaller than that number would seem to indicate. Once the bullet exits, the pressure vents and you get some jet effect that increases the motion induced by the imbalance in force that resulted from the bullet moving within the barrel.

Tuner,

The whole system is mechanical--including the spring. The spring is applying force to resist the recoil, and that force has an effect that can not be ignored. Any force applied against the recoil is going to slow the slide velocity and therefore delay unlocking. As jungle notes, putting your hand against the back of the slide can delay unlocking forever. Likewise, putting a MUCH stouter spring than called for would do the same. Any REDUCTION in force will allow the slide to move more rapidly and therefore speed unlocking. Putting no spring in there will get you the most rapid unlocking possible although in some firearms, the effects will be less drastic than in others for the reasons noted above.

It's worth noting that while we're all quite sure of our "theory"--so far no one has volunteered to shoot a Glock 10mm with Double-Tap ammo and no recoil spring installed. ;)

1911Tuner
January 20, 2006, 01:20 AM
Jungle, I see what you're saying. I really need to get a Glock on the bench and study on the timing events so I can give better answers when these kaboom questions come up.

John...To try another angle on the timing issue:

Chevy small block V-8, circa 1969. Your choice of CID, but I'm partial to the 302 and 327.:cool:

Crankshaft drives the camshaft. Camshaft drives the distributor. Distributor determines when the plug fires in degrees before the piston reaches TDC on the compression stroke. The higher the engine rpms, the faster the distributor spins.

If you disable the automatic spark advance built into the distributor and set static ignition timing at 10 degrees BTDC, the plug will fire at 10 degrees BTDC...regardless of how fast the distributor is turning.
(Yes, all you motorheads...I know that engine rpms will be limited if there is no spark advance. This is a hypothetical engine.)

If the barrel begins its unlock sequence at X amount of rearward slide movement, it's going to begin that sequence at X amount of slide travel, regardless of how fast or slow the slide moves...regardless of recoil spring tension, either in preload or its rating at full compression. It's a static, mechanically timed event. It has no automatic advance in relation to the slide speed.

The bullet must be gone BEFORE the barrel can unlock because of the force keeping the lug(s) pressed together as the slide and barrel are driven in opposite directions under full pressure...or even at 25% below peak. The link...in a falling link design...would be stretched and fail, likely before it could even budge the weight. Using Jungle's figures above...What do you think would happen if you tried to lift a nearly 2-ton weight attached to a barrel link by a 156 diameter pin on one end and to a cable and a .200 diameter pin on the other...at the speed that the barrel is unlocked and linked down in a live-fire event?

Can't happen, Kemosabe.

Even though the linkless barrel design is stronger than the falling link, it's not that much stronger that it could stand tensile stresses like that for very long.
And...even if it could, the front corner of the barrel lug and rear corner of the slide lug would be quickly abraded and destroyed being forced apart under that much force.

JohnKSa
January 20, 2006, 01:48 AM
Tuner,

Haven't you seen the pics posted on the 1911 forum showing that the slide has already move backward far enough that it has begun the unlocking process before the bullet leaves the muzzle?

jungle
January 20, 2006, 02:34 AM
John, I'd like to see those. Got them handy?

jungle
January 20, 2006, 02:53 AM
Here is a little greatly simplified math.

230grx800fps divided by 7000grainsx1.25lbs= This gives the recoiling mass a velocity of 21 ft per second and the bullet 800 ft per second. The bullet exits the bore moving about 4.5 inches and the slide moves rearward by .1181124 inches.

The actual answer is much more complicated because the bullet gains speed as it reaches the muzzle as does the slide, so the initial forces are very high, but acceleration takes time to build. The recoil spring also acts with increasing force to decelerate the slide, acting with it's greatest force at the end of recoil. This simple calculation does not account for friction or spring.
Remember that recoil can only be produced by velocity and as velocity builds to peak the bullet exits. The operation is by recoil. Also remember that a given force accelerates a lighter mass much more rapidly than a heavier mass.

Check back with Mr. Newton and keep that very high initial force in mind.

1911Tuner
January 20, 2006, 09:16 AM
Tuner,

Haven't you seen the pics posted on the 1911 forum showing that the slide has already move backward far enough that it has begun the unlocking process before the bullet leaves the muzzle?

Haven't seen it, John. If it's a Glock...How far does the slide move when it starts? And...If the unlocking starts before the bullet exits, the timing is outta whack. Think about what would happen to those lugs if they were pulled apart laterally under that much pressure. Lotta frictional load there...

1911Tuner
January 20, 2006, 10:46 AM
Went ahead and anticipated the response, so I wrote this up on a notepad for a copy/paste here. A brief description of the barrel unlock/linkdown timing event.
*****************

Barrel Timing, from a 1911 perspective. Not sure how it works in a Glock.

At 1/10th inch it starts. By .250 inch, it's all over. Barrel is fully
linked down and in bed.

The rear, lower barrel lug strikes the vertical impact surface high on the lug just as the barrel settles into the frame bed...or bridge. In a correctly timed and dimensioned gun, the lower barrel radius actually doesn't hit the bed,but rather sits above it by a thousandth inch or two. Most do hit the bed without problems...or seem to...but if the gun is "right" they don't.

If the vertical impact surface is too far rearward, or the lower lug is located too far forward...the barrels' rearward momentum is stopped by the link in tensile stress.(Stretching) Under this circumstance, the link will stretch or fail...depending on how far out of spec the dimensions are...at anywhere from 1,000-5,000 rounds, on average. I've even seen the lower barrel lug separate from the barrel in extreme circumstances.

Likewise...if the bottom of the barrel hits the frame bed BEFORE the lug strikes the vertical impact surface...the link and lug will come under stresses
that will stretch the link or cause the lug to fail. I recently
had occasion to repair a NRM Colt that had suffered a U-shaped crack in the floor of the chamber adjacent to the lower lug because the barrel was hitting the frame bed before being stopped by the vertical impact surface. According to the owner, the round count was somewhere in the 5,000-6,000 round mark.

If the barrel and link will fail under these circumstances...due to the barrel's rearward speed and momentum alone...how quickly would one or the other...or both...fail if they were forced apart under locking pressure? Answer? Best WAG would be within 500 rounds..and probably much earlier.

Although the Glock is probably somewhat different in the specs and dimensions, it's still basically a modified copy of the Browning tilting barrel
design, and functions in basically the same way. i.e. Locking lugs engage
under firing pressure...front barrel lug face against rear slide lug face in a
20,000 psi tug of war. Forcing them apart while under that much pressure would do a lot of damage to both pretty quickly. Corners would be rolled.
Tensile stresses would cause the "pulling" parts...lower lug, link and slidestop pin to stretch and/or fail.

Unlock while the bullet is still in transit? Not without damage, mah brother.
****************

Jungle provided:

230grx800fps divided by 7000grainsx1.25lbs= This gives the recoiling mass a velocity of 21 ft per second and the bullet 800 ft per second. The bullet exits the bore moving about 4.5 inches and the slide moves rearward by .1181124 inches.

Those figures sound about right. The unlock event begins at about
.100 inch...nominally...in a 1911. It can be a bit earlier or a bit later, but in any case, the bullet must be gone and pressure at atmospheric
before the barrel can unlock and allow the breech to open. If this unlock/opening occurs while the bullet is still present and the pressure is high...damage to the gun and likely case failure will result.

jungle
January 20, 2006, 12:19 PM
Springs may lend a little to the effective slide mass, but consider this. Take a look at various tilting barrel designs. As caliber, weight and velocity go up, slide mass is increased. The Glocks in 10mm have slides that are heavier. It will also be noted that spring weight is not increased much, because it can, if too heavy, contribute more problems on the feed cycle than help on the recoil cycle.

In shorter versions of the same pistol, having a lighter slide, the spring weight may increase to slow slide velocity, but it is primarily the unlock timing which is altered to keep everything under control. On a 1911 this is seen on the bottom barrel lugs, on a Glock it can be controlled with the locking block and barrel cam.

After reading back through the original poster's statements it is obvious this pistol works fine with "wussy" factory loads, and whatever caused the problem is generating much higher pressures than design intent. Read POST #33.

It will be apparent to anyone who has slogged through all this that timing has limits. If the mass and velocity design parameters are exceeded, damage will occur.
That 20MM round is going to need a great deal of mass or gas or electric operation.

1 old 0311
January 20, 2006, 12:21 PM
I thought ALL plastic guns did that:neener: :neener: :neener: :neener:


Kevin

jungle
January 20, 2006, 01:01 PM
I'll be happy to fire a 10mm Glock without a recoil spring if you'll let me use a rubber band of enough strength to hold the slide shut as the striker is cocked. A short length of spring or buffer material is a good idea to slow the slide at the end of recoil, but for a one shot demo will not be necessary.

1911Tuner
January 20, 2006, 02:43 PM
Jungle observed:

>Springs may lend a little to the effective slide mass, but consider this. Take a look at various tilting barrel designs. As caliber, weight and velocity go up, slide mass is increased. The Glocks in 10mm have slides that are heavier. It will also be noted that spring weight is not increased much, because it can, if too heavy, contribute more problems on the feed cycle than help on the recoil cycle.<

Precisely!

And:

>>In shorter versions of the same pistol, having a lighter slide, the spring weight may increase to slow slide velocity, but it is primarily the unlock timing which is altered to keep everything under control. On a 1911 this is seen on the bottom barrel lugs...<<

Again...Spot on. The other side of the problem with the short 1911 variants is that the short barrel requires a longer arc and steeper angle in relation to the slide axis...which means that the barrel has to unlock a bit earlier than the longer versions, and it has to drop fast. I've run into several timing issues with pistols that have barrel/slide lengths below Commander class...
and it's always early unlock timing. Few have been so early that damage was done to the upper lugs, but often early enough to stretch the link and/or crack the lug at the rear of the junction with the barrel. The first warning sign with these is the "Tadpole Tail" primer indent...something that the Smith
.40 DA pistol was known for early on. Long, flat pressure curve + early unlock
timing=problems. Handloaders found that they could usually lose the primer mark by using a quick powder...on the level of W231 or faster. We also noticed slightly bulged cases on occasion...and we saw some locking lugs with radiused front corners too. On guns with reduced chamber support, all it takes is for the headspace to be a little too close to max to produced bulged cases. If it happens to go out of spec by just a little, they can blow with certain brands of ammo.

jungle
January 20, 2006, 08:19 PM
Much has been said about springs and their effect on slide movement, but the spring's other end is tied into the frame. In a sense during recoil the spring acts as an elastic connection from the slide to the frame and shooter, boosting the effective mass of the slide and allowing energy it can't absorb to transfer through the frame to the shooter.

JohnKSa
January 21, 2006, 02:50 AM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

http://www.tbullock.com/images/flash/45-slide-l.jpg

Look closely--that's the bullet about 0.3" in front of the barrel. Actually it's only 0.16" or so forward of where the muzzle WAS upon firing--the muzzle/slide has already moved back about 0.16" in recoil.

http://forum.m1911.org/printthread.php?t=1950&page=2&pp=10

The guy who posted the pic ALMOST has it right, but he handwaves a bit too much. Here's his quote:the slide has recoiled about 0.16 inches while the bullet was still inside.
The slide and it's attached parts weigh 17.5 ounces; or 7660 grains, and the bullet travels 4.4 inches. 4.4 x 230 / 7660 = 0.13 inches.
The reaction of the gunpowder accounts for the rest.That 0.03 inches that he handwaves away is equivalent to adding nearly 50 grains of weight to the bullet side of the equation--that's WAY too much to be dismissed as "the reaction of the gunpowder". This is a classic example of having made the conclusion first and basing the interpretation of the experiment on the desired outcome.

That 20% or so that is being dismissed is most reasonably attributed to the retarding force of the recoil spring. It's clearly applying force to slow the slide velocity--that makes a heck of a lot more sense than saying you can account for a 50 grain weight increase to the bullet side of the equation by factoring in the effects of about 5 grains of powder and totally ignoring the recoil spring force.

BTW, I believe a fairly well respected authority makes the comment earlier in the linked thread (and on this thread) that 1911 unlocking begins at about 0.10" of slide travel and then later in the linked thread says that some delay as much as 0.125 inches. That would mean that the measured travel in the photo--0.16" is WELL into the unlocking phase--unlocking is definitely progressing and is well underway.;)

That also fits reasonably well with jungle's rough calculations indicating that the bullet exits when the 1911 slide has travelled about 0.12"--already into the range where unlocking is happening.

Ok, so let's assume that the 20% that the photo taker handwaved is a combination of the recoil spring's retarding force, and the retarding force of the hammer cocking action. If we remove both of those effects (as might be the case in a Glock with a worn out recoil spring) that means that the slide has travelled around 0.13" (unlocking is definitely started) and the bullet still hasn't exited the barrel. There's no question we're getting well into the unlocking process with the bullet still in the barrel.

atblis,

Do you have the means to precisely check the case head to see if it is perfectly square with the cartridge walls? If it's no longer square, that could mean there was still significant chamber pressure when the slide & barrel unlocked. I don't know if there is enough of an effect to measure, but it's an interesting thing to check...

1911Tuner
January 21, 2006, 08:41 AM
Looks about right, John...but if the Glock is starting to unlock before the bullet exits, it's not operating correctly. The forces that are keeping the
locking lugs butted together are too high to allow the lugs to be pulled apart
without damage.

Drill a hole in a steel disc and clamp it in a vise, covering about the same surface area with the vise jaws as a locking lug...or roughly a half-inch or so square. String a steel cable through the disc and pull on it hard enough
to free it from the jaws. Do that over and over...and it won't be too long before you start seeing the effects on the disc.

Now...I realize that the lugs aren't captive on two sides. The experiment is
to demonstrate the frictional forces required to pull the flat-faced objects apart that are under that much pressure. Keep in mind too, that during the
slide cycle, that it's also not a simple matter of just pulling them apart. The slide continues to hurtle backward as the barrel lug is pulled free. That subjects the top corner of the lug to a scizzor-like action as the slide lug passes over it. The action would round off the corners fairly quickly if the barrel was being pulled downward under that much pressure.

Also...Haven't fetched the caliper yet to verify...but the base of the bullet in the photo looks to be quite a bit further out than an eighth of an inch. If the witness tape is truly .160 inch apart, the bullet appears to be roughly 50%
farther than that from the muzzle. hard to see exactly where the base is, but that's as near as I can tell by eyeball check. I'll try to do that later, and
Jungle can recalculate by working his equation backward to see where the
slide was at the point of bullet exit.

I'm still gonna call this bulged case as a headspace problem. If the owner has it checked with a standard gauge set...we'll know.

jungle
January 21, 2006, 08:47 AM
John, That is an interesting photograph in several ways.

1. Take a look at the barrel in the ejection port, it still appears to be locked by the angle in relation to the slide. Various combinations of link and lower ramp configurations can alter the unlock difference from .1 to .125 or more. I don't have the means to measure the travel handy from the photo.

2. It is curious that the total travel at .16 is even higher than the calculated travel without friction or springs. The ejecta from the gases would only account for 5-6 grains at 4700fps or so, not enough to make a big difference.

3. Why did the travel exceed the calculation? Is the barrel unlocked? Why didn't the spring reduce the travel beyond the calculated value? Was there any evidence of damage?

4. You seem to be claiming the spring caused additional movement rearward. Is this correct?

jungle
January 21, 2006, 09:23 AM
This is getting interesting. More math.

230grsx800FPS + 5.6grsx4700FPS divided by 1.09375x7000=27.1FPS slide velocity=.146625 slide travel.

The 5.6x4700 accounts for the gases and their exit speed, we used a lighter mass in this equation-17.5 oz is 1.09375 pounds. Slide speed went up, yet we still get a value lower than what is claimed with springs and friction?

I am of the opinion that the actual unlock is happening a little further back than first thought. If the spring is having an effect it would seem it is helping to move the slide to the rear and we know that isn't right. Higher velocity of the bullet? What was the spring weight in the pistol?

To me, the strongest evidence that unlock hasn't begun yet is the angle of the barrel in the ejection port, it is still looking locked.

There is another photo on the first page of the link you provided that shows the barrel parallel to the slide in an unlocked position.

redneck2
January 21, 2006, 09:55 AM
UH, I'm just a simple country boy but I've got an idea.

Take the same ammo and shoot it in another G20. Take some different ammo and shoot it in the subject gun. Instead of doing hours of calculations you could find the answer in 5 minutes. But, what do I know? I'm just a pig farmer from Indiana.

FWIW, I've got a G20 thats popped off some smoking, and I mean smoking rounds. Ones that are equivalent to Double Tap.

I examined the cases under a magnifying lamp and never did find "the bulge". What does that mean??? It means my G20 doesn bulge cases. Yours might.

1911Tuner
January 21, 2006, 10:05 AM
Jungle...you may be right about the angle of the barrel. Hard to tell, since it drops so little for the total travel, that determining the very beginning is something that is best measured with a pair of dial indicators....one at the rear of the slide and one on the top of the barrel. If the second needle budges even .001 inch...you've gone beyond the start of the sequence.

The sequence begins just at the point of link's arc that puts it AT the correct point and angle to unlock...and all the slack has been removed from the
clearance between the link holes and both pins...which can vary from gun to gun. It doesn't mean that the barrel has actually moved, nor has tensile
stress begun. It only means that the slide and barrel are in position to begin the sequence. All that takes time. Meanwhile, the bullet is screamin' toward the muzzle at velocities approaching 800 or so fps. GI Hardball specs call
for 830fps +/-25. Most of the popular factory hardball these days runs in the
800-825 fps range, and the 230 hollowpoints are from 850-870 fps.

Looking at the recoil spring's influence...The standard 16-pound spring has an
in-battery preload value of about 3.5 pounds +/- a few ounces. If we plug in a linear resistance...which it probably isn't...and use the rated 16 pounds for the other end of the calculation... .100-.120 inch of slide travel just isn't going to provide a helluva lot more resistance to the slide. Rough figures here...12 pounds of additional resistance in 3 inches of slide travel equates to
4 pounds per inch...or maybe a half-pound of extra resistance.

Note the many hundreds of IPSC limited shooters...basically the stock class...
who juggle recoil spring rates...generally much lower than the standard 16...
in order to keep the muzzle from dipping below their line of sight when the slide returns to battery, for follow-up shots. These guns fire many thousands of rounds per year...in competition and in range practice...yet they don't produce the bulged and blown cases that we see in these photos. Why? Headspace has a lot to do with it.
Even though the guns compete in the "Stock" classes...many are carefully built with match-grade barrels in which headspace usually runs close to minimum specs, or even below. For the ones that aren't...a bulged case
is a sign that there's something seriously wrong with the gun, and the shooters have the problem corrected...or at least they do if they've got sense enough to come in out of an electrical storm. Problems that a new or heavier recoil spring can't correct. I'd go a step further and suggest that if any gun is on such a fine line that a simple recoil spring change will take it from safe to dangerous...and bulged cases are dangerous...there is something seriously wrong with the design or the specs of the gun.

jungle
January 21, 2006, 10:19 AM
The guy doing the math in the link provided comes up with the right answer but doesn't show the equation correctly and then goes on to point out that velocity doesn't matter. Wrong.

I see the photo, but whether it is an unlocked or unlocking or locked barrel is not completely clear.

redneck, You sir, have common sense and that is an uncommon virtue. I suggested such a test earlier with no response, in the meantime we are just chewing the fat and trying to figure out how these things work.

Tuner, Agree, but let's not forget the term Superface, which originated when those near perfect guns encountered ammo that exceeded a very high limit.

georgeduz
January 21, 2006, 10:21 AM
very well said 1911tuner.

1911Tuner
January 21, 2006, 10:33 AM
Okay...Marking the distance from the base of the bullet to the muzzle as near as I can see by using the rear point of the cigar-shaped bright spot on the side of the bullet to mark the base...and comparing it to the tape marks on the slide and frame...the bullet is nearly twice as far from the muzzle as the
distance between tape edges. If the witness marks are truly .130 inch apart...and assuming that my assumption on the bullet base are a bit off...
the slide had moved about .070 inch when the base of the bullet was just at the end of the muzzle...at the point of breaking into air.

Another point that's been overlooked in the pressure and unlock debate is that, the rifling isn't cut all the way to the edge of the muzzle because of the slightly countersunk crown. Gasses would start to vent, dropping the pressure before the bullet base is dead flush with the edge of the muzzle...so we're probably back to roughly .060 inch of slide movement at bullet exit...or maybe less. Without measuring, the crown on the Kart barrel in my Springfield
looks to be about .030 inch deep. Adding that distance to the approximate
point of slide travel when the pressure starts to drop...the bullet has exited
about a 32nd inch earlier than the photo suggests.

Jungle...If you can follow all this without gettin' Excedrin Headace #1911,
plug the figures into your equations and give us a final score!:cool:

jungle
January 21, 2006, 10:52 AM
Tuner, Going to stick with my figures, which were predicated on the bullet base being at muzzle for the slide travel distance given, but I do believe that friction(slide, magazine round to slide, barrel to bushing, and whatever else is there) may contribute 10-20% to the mass, and therefore reduce slide travel somewhat.

The fact that it all works and works well with a fairly wide variation in spring is telling. The equations came from a former head of Army Ordnance and I do believe he knew what he was doing.

Haven't weighed the Glock recoiling mass(nor the 1911s for that matter, just going on what was given), but I'll bet the Glocks is heavier than the 1911s, being quite a bit thicker and lacking the restraint of the 1911's hammer.

1911Tuner
January 21, 2006, 11:07 AM
Jungle...Look closer at the bullet base in relation to the edge of the muzzle.
If you lean to the left a little, you can see the base a little more clearly.
It's at least 75% further from the muzzle as the distance between the witness marks...and that's not even accounting for the muzzle crown.

You can also do a direct ratio equation. Mike the length of a 230 hardball bullet, and take measurements on the gun pictured. Apply the direct ratio to determine more closely where the bullet base is.

When you find the bullet base, use a scale to measure it as closely as you can...then do the same with the tape, and compare. Then, if you're inclined...add another 32nd inch to the distance that the bullet has moved
from the muzzle...the point that gasses began to vent into the air.

I've worked with Navy Ordnance myself...and found that some of those boys really didn't have a clean grip on how the thing works until some of the old armorers finally got'em clear on it.

oorah...:cool:

jungle
January 21, 2006, 11:26 AM
I see what you are saying, but also consider what a bullet would do leaving an unlocking barrel- accuracy would be in the crapper and the amount of unlock would not be consistent, not to mention the wear and tear. It isn't happening and it wasn't designed to.
A rough ratio of bullet movement at 800FPS and slide movement at 27.1 FPS could be juggled around, but it isn't going to change much.
I've been flying all night and this has been fun, but I've got to hit the rack.

1911Tuner
January 21, 2006, 11:44 AM
I see what you are saying, but also consider what a bullet would do leaving an unlocking barrel- accuracy would be in the crapper and the amount of unlock would not be consistent, not to mention the wear and tear. It isn't happening and it wasn't designed to.
A rough ratio of bullet movement at 800FPS and slide movement at 27.1 FPS could be juggled around, but it isn't going to change much.
I've been flying all night and this has been fun, but I've got to hit the rack.


I understand...Did the Midnight Killer Shift for 15 years myself.

You said:

>I see what you are saying, but also consider what a bullet would do leaving an unlocking barrel- accuracy would be in the crapper and the amount of unlock would not be consistent.<
*******************************

Exactly so. That's part of the reason that match pistol armorers delay the
unlock for as long as possible...to get the bullet closer to the muzzle before the barrel starts to drop. The other part being that they want primary extraction to begin in a straight line, before the barrel starts to drop. Of course, on doing that...because it was delayed...once the unlock starts, the barrel has to drop quickly in order to get out of the way.

In any case, if this photo is a pretty close representative of the event...the bullet has broken free into the air at a maximum of about .075 inch of slide travel...well before unlock starts. Looks like we're on the same page. Now all we gotta do is beat John with a brickbat until he can see it.:neener:

JohnKSa
January 21, 2006, 07:26 PM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.the the bullet has broken free into the air at a maximum of about .075 inch of slide travel...well before unlock starts.That incorrectly assumes that the slide and bullet are travelling at the same velocity and they most certainly are not.

The picture shows the bullet about 0.3" in front of the barrel. And it also shows that the slide/barrel combo has recoiled 0.16" from battery. (According to the picture taker, the witness marks are 0.16" apart, NOT 0.13".)

The bullet has travelled about 4.4" in the time it took the slide to travel 0.16 inches. The bullet is travelling at LEAST 27.5 times faster than the slide. Jungle's calculations say that the rough number is closer to 29.6 times faster.

Moving the bullet back about 0.3" to put it back at the point of exiting the barrel is equivalent to moving the slide forward by about 0.01 inches--it's moving much slower than the bullet. That puts the total slide travel at the exit point at about 0.15" of rearward movement which is still WELL into the unlocking process according to our expert. ;)

I'm not claiming that these calculations are exact, but they are close enough pose a serious challenge the idea that the gun has not begun unlocking before the bullet exits.

If you take away the other retarding influences on slide motion (recoil spring & hammer cocking effort) then it's only going to make the unlock come earlier since you're increasing the slide velocity.match pistol armorers delay the unlock...to get the bullet closer to the muzzle before the barrel starts to dropIsn't this an admission that it is accepted by match pistol armorers that the gun is unlocking with the bullet still in the barrel? Just as the photo suggests?These guns fire many thousands of rounds per year...in competition and in range practice...yet they don't produce the bulged and blown cases that we see in these photos.I believe that a very reasonable explanation for at least PART of this is that you're talking primarily about .45ACP pistols operating at 21Kpsi, not 10mm pistols operating at 37.5Kpsi--that's a 79% increase in pressure.

jungle
January 21, 2006, 07:43 PM
John, Many of the competition shooters were using rounds that exceeded .38 Super and SAMMI specs by a fair amount. This continues today with certain rounds. The bulging exists in certain guns because of a couple of factors.
1. Some guns have too much throat and that allows a bulge at a certain pressure level. This will be increased if excess headspace exists.

2. No matter how well the gun is built and assuming it stays locked, the brass will always be the first thing to fail if pressure is too hgh. This is true for bolt guns and recoil operated pistols.

JohnKSa
January 21, 2006, 08:11 PM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

jungle,

Couple of questions--I can't really tell your position on all of this.

1. Do you concur that the evidence supports a reasonable conclusion that the 1911 in the picture is already unlocking (or at least beginning to unlock) before the bullet exits?

2. Do you think that early unlocking CAN cause, or at least exacerbate, case bulging?

3. Do you believe that altering the recoil spring weight can speed or delay unlocking?

I don't know for sure exactly what's going on with the excessive case bulging. I know that not all Glock 20 pistols bulge cases, and I have a hard time believing that we're seeing huge headspace variations in factory pistols. That sort of thing leads to lawsuits. Perhaps there are minor headspace variations whose effects are amplified by weak/worn-out recoils springs?

1911Tuner
January 21, 2006, 08:29 PM
John, no. The bullet has traveled over 5 inches in the time it takes the slide to travel .075 inch...and the bullet is about twice as far from the end of the muzzle as the slide has traveled in the picture. It takes a little suintin' to see where the bullet bas is...but you can see it if ya squint long enough.
The bullet broke free...according to my redneck figgerin'...at around .075 inch
of slide travel.

Match armorers delay the barrel unlock and linkdown mainly as an extra precaution of ANY barrel movement...not to keep it from unlocking before the bullet exits. They want to keep it solidly locked and fully supported at the lockup points...as solidly as it is on ignition. Remember...the locking lugs aren't truly locked until the gun fires. They're touching under mechanical
pressure before ignition...whatever the recoil spring tension affords...but not pressure-locked.

Havin' a hard time tryin' to find a way to explain this...but I'll try it again.

The locking lugs...slide and barrel...are butted together under intense pressure. Something on the order of 20,000 psi. Barrel nailed forward...slide hammered backward. The pressure is trying to shear the lugs off the barrel
and out of the slide...under some 10,000 pounds of pressure, if we assume a half inch square of surface area. The link, link pin, and slidestop pin simply aren't up to the task of forcefully separating the lugs for thousands of rounds
under that kind of pressure. And...even if those components were able to withstand that sort of tensile stress...once the lugs disengaged, the slide lugs would rake across the barrel lug corners as the slide hurtled rearward. Press your hands together hard and have someone jerk one of your arms down until your hands disengage. That is what would happen if the barrel could be unlocked under pressure, and the corners of the lugs would be eaten away quickly.

Again...Visualize trying to jerk a 5-ton weight off the ground by a barrel link,
attached to the weight by a .156 diameter pin on one end and a .200 diameter pin on the other. Somethin's gotta give...and it won't be the weight.
Even imagine trying to drag a 5-ton weight...which would be a closer approximation of the event...by the link and the two pins. I've seen half-inch
steel cables on a tow truck snap while trying to upright an overturned car that weighed less than half that. I'd venture a guess that those cables are quite a bit stronger than that tiny link and the pins.

There's probably a formula to determine the frictional resistance of trying to
separate a half square inch of surface under 5 tons of compression...but I don't know what it is. Jungle? You seem to have a good handle on the math.

jungle
January 21, 2006, 08:31 PM
John, Here is what I think.

1. The photo doesn't show us enough to conclude whether the pistol is locked or in some stage of unlock.

2. I think the bulges seen are for the most part caused by excess pressure in combination with excess throating, either of these can cause bulging and together they make it worse. It is a dangerous condition. Headspace problems will make it worse.

3. I believe spring weight has little to do with unlock timing.

4. Tilting barrel recoil operated pistols by design intent delay unlocking until pressure is well below that which would cause a case to bulge.
The bullet leaves the barrel before unlock happens.

1911Tuner
January 21, 2006, 08:41 PM
Okay...On to the other question:

"I have a hard time believing that we're seeing huge variations in headspace..."

Believe it, mah fren. I've seen static headspace vary as much as .020 inch in
new and/or lightly used Colts. Seen several brand new pistols go to battery easily on SAAMI standard NO GO gauges...pistols that would have failed and been returned to unit armorers for repair...and Colt doesn't have the market cornered on this observance. In these...all it would take is a little over-zealous barrel ramping and throating to produce bulged and blown cases...
and several have.

Why don't more pistols with max headspace bulge or blow cases? Simple.
Headspace can be excessive because the chamber was cut too deep,
and the case just moves further forward...or it can be out in the other direction...in which the case moves backward when the gun fires because
the breech is partially open under pressure as the slide is driven backward.
The case follows the slide...exposing the thin area forward of the web...
and it balloons. Sometimes the pressure exceeds the elastic limit of the brass...which varies with case construction and material...and it blows out.

JohnKSa
January 21, 2006, 08:53 PM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.The bullet has traveled over 5 inches in the time it takes the slide to travel .075 inch...Ok, the picture taker claims that the measured slide travel in the photograph is 0.16 inches. I don't think that is in question, it can be verified by reading the original thread, or if we need to, we can extrapolate the actual number by measuring parts of the gun in the photo and doing a comparison.

The bullet can be seen in the picture, and one can see that the base of the bullet is about twice as far from the end of the barrel as the slide has travelled. I believe we are also in agreement at this point. Using the slide travel number (provided by the person who actually took the picture) as a reference, we are force to conclude that the base of the bullet is about 0.32 inches from the end of the barrel. Still in agreement.

That means that to get the bullet back into the barrel, we need to move it backward by about 0.3 inches.

The picture taker says the bullet has travelled 4.4 inches, you say 5 inches. Whatever--by the picture taker's numbers the bullet is travelling 27.5 times faster than the slide, by your number for the bullet travel distance, it's going 31.3 times faster, by jungle's calculation it's going 29.6 times faster. I'll use your number. That means that at the point in the picture, the bullet is travelling about 31.3 times FASTER than the slide.

If you're going to move the bullet back 0.3 inches to get it back into the barrel, you have to move the slide forward a corresponding amount since both objects are moving in the picture. If the bullet moves 0.3 inches then the slide, which is moving 31.3 times SLOWER than the bullet, moves a distance that is 31.3 times SHORTER--that would be about 0.01 inches using your number for bullet travel.

So, we have now moved the bullet BACK by 0.3" to get it back into the barrel and moved the slide/barrel FORWARD 0.01 inches from their positions in the picture. Since the picture taker says the slide is positioned at 0.16 rearward in the picture, moving it forward by 0.01 inches puts it at 0.15 inches when the bullet is exactly at the point of exit. 0.15" is well into the unlocking process according to your numbers.

Rather than simply saying "No", please point to the problem in this math and we can go from there. ;)

Jungle,

I would invite you to do the same.

jungle
January 21, 2006, 09:06 PM
John, I don't fault the math or the distance the photo maker measured, but it is entirely possible that that particular pistol's slide has to travel a little further than the norm to unlock and it is impossible to conclude from the photograph exactly in what stage of lock/unlock this pistol is in.

Let us presume for a moment that the bullet still has an inch to go to exit the barrel and unlock is complete at that point. Examine a pressure curve and note that pressure is highest just as the bullet starts to move down the barrel and then ramps down rapidly as the bullet travels down the barrel and velocity builds. Even if this unlock happens with the bullet yet to travel an inch to clear the bore, the residual pressure would not be enough to bulge the case.

In considering time of travel we have assumed 800fps, but an argument could be made that the average velocity is 400fps= 0 at start and 800fps at finish, a simplification that doesn't depict what happens, but one that could skew the velocity of the slide quite a bit in the early stages of movement.

JohnKSa
January 21, 2006, 09:28 PM
jungle,

According to Tuner's numbers, 0.15" of travel is well into the unlocking cycle. He lists 0.125" as being sort of an outside limit for the beginning point of unlocking with 0.1" as being the normal start. I think we're sufficiently OUTSIDE of his listed outside limit to be pretty comfortable saying that the pistol is already unlocking.skew the velocity of the slide quite a bit in the early stages of movement.Agreed, but we're not examining the early stages of slide movement. At the point the picture was taken, the slide and bullet are both at maximum velocity. So at best, I'm going to underestimate the amount of slide travel. Furthermore, your numbers based on accepted/typical slide/bullet velocities agree well with the numbers provided by the picture taker that I am using. Everything about the picture supports the numbers as I've laid them out, and while I don't think we can expect exact results, the margins are sufficient to support the conclusion I've reached.

For the bullet to exit before the slide reaches the 0.125" travel point that Tuner says is pretty much the outside limit, we'd have to have the slide moving 3.5 times slower than what the picture suggests--or about 7.7fps at the point of MAXIMUM slide velocity. If you play around with those numbers, you end up having to say that it takes more than an eighth of a second for the slide to cycle--way too slow. It's even worse if you assume that the pistol was already unlocking around 0.1" of travel. You'd be saying that the maximum slide velocity is only 5fps and that it would take around a fifth of a second for the slide to cycle.

Here is an independent mathematically intense post on another forum that basically verifies my analysis of the photo.

http://forums.1911forum.com/showthread.php?t=2977&pp=25

It also concludes (and the numbers are remarkably similar) that unlocking has begun before the bullet exits. His numbers show bullet exit takes place at about 0.13" of rearward slide travel. His calculated value for slide velocity (25.7fps) agrees well with the number extrapolated with the picture. His calculation also suggests that spring forces are applying over 9lbs of force at the moment of firing--also agreeing well with my estimates.

jungle
January 21, 2006, 09:41 PM
John, Just to clarify, your conclusion is that the bullet always exits in this type of pistol after slide unlock is complete? Or the bullet exits sometime during the unlock process? And bulging is because high slide velocity speeds unlock? High pressure, headspace and throating are not factors?

From a mechanical standpoint, unlocking gets easier as pressure drops and as the bullet nears the muzzle it is valid that pressure has dropped off 90% or so. If the pressure has dropped that much, how can it bulge the case at that point.

1911Tuner
January 21, 2006, 10:00 PM
I ain't gonna argue with numbers too much. I'll let the mathematicians duke it out instead...but I will add that, in a measured time/distance experiment on a .45 caliber 1911 pistol, the average slide speed for the return to battery event was just a tick under 3 fps. (Wish I could remember where I read that...but it was on one of the forums.)


Three...fps. If we assume that the return to battery takes 2.5 or 3 X the amount of time that it takes the slide to complete the recoil cycle...7-8 fps isn't too far off the mark for the first 1/8th inch of travel.

John...You still don't seem to be considering the high load and frictional forces
that nail the locking lugs together. The link just can't jerk'em apart without snappin' like a twig. One sure way to find out is to take a link to a community college where MET is offered...and visit the metallurgy instructor.
They have a hydraulic tensile stress testing machine...or they should have.
Take'em a link and have'em test it as part of a class. I'd be interested in knowing how much stress it takes to break one. Bettin' that it'll break under a helluva lot less than 5 tons though...

JohnKSa
January 21, 2006, 10:02 PM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

jungle,
The statement has been made repeatedly on this thread (and others) that it is impossible for the unlocking process to begin while the bullet is still in the barrel.

I think it's clear from the photo (and the other mathematical analysis in the second link) that 1911 unlocking DOES start with the bullet in the barrel at least some of the time. I think that makes it reasonable to assume that is also the case in other roughly similar designs.

I think that (depending on a lot of factors) sometimes the gun hasn't started unlocking, sometimes it's in the process, and sometimes it's completely unlocked by the time the bullet leaves the muzzle. I think that the latter case is probably unusual and likely to cause noticeable problems. However, clearly, the rigid stance that unlocking can't start while the bullet is in the barrel isn't supportable unless you work very hard to explain away the evidence in the picture.

That means that any analysis based on or depending on the idea that it's impossible for the gun to begin unlocking with the bullet in the barrel needs to be re-evaluated.

I think there are lots of things that contribute to case bulging, and your list seems reasonably complete. However, an earlier statement in this thread said that recoil spring tension was a non-factor in case bulging. I think that the analysis shows that it is unreasonable to completely rule out recoil spring weight as a contributing factor, but also shows that, in general, other factors must be present for it to become an issue.

Tuner,

3fps is way too slow and is not supported by the math. There are POINTS during the travel where it is that low but not at the point where the bullet is just leaving the barrel.

Ok, here's my whole point. You started with some basic assumptions. Your arguments throughout this thread are based on using your initial assumptions to explain away the evidence in the picture. That's not the way to look at an experiment. You can't interpret experimental evidence with the idea that you won't allow any of the conclusions to change or challenge your initial assumptions.

I understand your reasoning on the high load/friction thing, but I reject the conclusion because it is not consistent with the photographical evidence as supported by the mathematical analysis. It fails the test because it contradicts clear experimental evidence.

Obviously unlocking can start with the bullet in the barrel--I would say that evidence in combination with your comments about high friction due to pressure retarding the unlocking that drive us to the conclusion that either the pressure (and therefore the friction) has dropped significantly by the time the bullet is near the muzzle, or that there is something more to understand about how the pressure in the barrel affects the unlocking timing, or maybe even there's something we're missing altogether...

Ok, I learned some stuff on this thread...

In light of what I've learned from the photo (and the subsequent discussion), I would have to go back on the implications of my initial comment on this thread and say that the bulged cases that started this thread are not due exclusively to a worn out recoil spring or an under-sprung gun--in fact, the recoil spring tension is probably not even a major contributor to the problem. While the recoil spring can be a contributor, the evidence does not support it's being a major contributor. The gun in question has some other problems, and they need to be addressed before the gun is shot with any more hot loads.

jungle
January 21, 2006, 10:15 PM
John, The Link to TiroFijo's post in Post#93 is quite clear and one of the best reads on the subject. He is a formally schooled engineer and a spring specialist. I urge everyone who is interested to read it carefully.

His conclusions?
Springs don't effect the unlock timing to an appreciable degree. The bullet leaves the barrel prior to unlock unless something is abnormal with the design.

His writing and understanding is the very best I have ever seen and his treatment of springs is more complete than most.

1911Tuner
January 21, 2006, 10:17 PM
John...Read my last post.

Nobody said that the recoil spring could be completely disregarded. Nothing can be completely disregarded. Anything that CAN have an effect on the slide will do just that. Nothing means everything, but everything means something. The spring's effect on the TIME that it takes for the slide to move that first .100-.125 inch is so negligible that it almost can be disregarded though...at least in a recoil-operated pistol. "Time" and "Timing" are related, but they're not the same.

Straight blowback...Yes. Spring tension and slide mass are all that keep the breech from opening under pressure...and a 10% reduction in spring load can make a serious difference.

My stance is that the recoil spring's effect on unlock TIMING is a non-issue, because the unlock timing is a mechanical event. It will occur at the same point, regardless of how fast or slow the slide moves. All it has to do in this instance is NOT to reach it while the bullet is still present, and pressure is high.

Yes...Delaying or advancing the slide position in relation to the bullet's position can make the difference between safe function and unlocking while pressure is high...but the gun would have to be right on the peg, and if it did unlock under pressure, case bulging and/or gun damage would be the result.

1911Tuner
January 21, 2006, 10:21 PM
That's the one! Thanks Jungle...:cool:

JohnKSa
January 21, 2006, 10:47 PM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.The bullet leaves the barrel prior to unlock unless something is abnormal with the design.Concur--but he also concludes (as I did based on the picture evidence) that the barrel definitely BEGINS unlocking before the bullet leaves the barrel. His numbers agree very well with what the picture shows. The bullet leaves the barrel pretty much in the middle of the unlocking process according to the picture and TiroFijo's calculations.

He does comment that the 9-10 lbs of force exerted by the recoil spring is not a major contributor but stops short of saying it is "negligible". His numbers put its effect somewhere around 10% of the equation, if I'm reading things right which agrees pretty well with my earlier WAG that the combined effect of the recoil spring & hammer cocking force were about 20% of the equation. I'll admit that it's not as much as I had expected, but I think that calling it negligible is a bit of an exaggeration.

I think what we've come down to is that if the gun has other problems such that it's on the hairy edge of being really messed up, you might be able to keep it on the safe side with recoil spring tension. However, if you're finding that the gun is showing alarming symptoms everytime the recoil spring gets weak, there are deeper problems that need to be addressed.

jungle
January 21, 2006, 10:53 PM
John, I think all of us have learned from the postings here and it has been a pleasure talking to all of you.
When we look at various sources for the truth and think about the problems, we all gain knowledge. It isn't about who is right, but what is correct.
This little arcane corner of knowledge may not be important to many, but for us it leads to a more complete understanding of something that interests us and that is enough.

1911Tuner
January 22, 2006, 05:19 PM
"He does comment that the 9-10 lbs of force exerted by the recoil spring"
*********************

It's not the loading of the spring in the in-battery position that's negligible.
It's the *difference* between the static, in-battery loading and whatever extra load is imposed after just 1/10th inch that doesn't have much effect.

I wouldn't put it as high as 9 pounds static/in-battery. CLoser to about 4 or 5, depending on the spring...but assuming that Tiro is correct, that would mean that the spring's rate is something on the order of 2 pounds per inch.
A tenth-inch of travel would add 2/10ths of a pound of extra resistance on the slide...or about the amount of force it takes a 10 year-old kid to blow out the candles on a birthday cake.

It's been a good discussion, gents! Jungle...Thank you for your participation, sir. John! Enjoyed the lively debate, as always! And...as always...a worthy adversary. We really gotta do a shoot, real Lexington-Style barbecue, and copious amounts of my infamous killer Turbocoffee one day! Jungle...You're invited as well.:cool:

Thegman
January 22, 2006, 06:25 PM
I've dealt with this for years, along with the folks that get pissed when anyone says anything percieved as "negative" about Glocks. However, I've taken the time to make careful measurements to determine the casue of the "Glock bulge". Here's what I found from my (and other's) Glocks I've examined:

1. Not all Glock calibers are the same with respect to bulge issues. Glock 9mm chambers seem to offer excellent support for the case and are relatively tight. The 9mm round is slightly tapered and Glock 9mm chambers seem to be cut to fit the round relatively snugly. However, Glock seems to taper the chambers of other calibers as well, perhaps for feed reliablilty. My 10mm Glock chambers taper at about the same ratio a do 9mm chambers, however, 10mm (and other cases) aren't tapered, which seems to lead chambers that are, IMO, excessively loose at the rear portion of the chamber. IME, this leads to (2).

2. The high pressure rounds (10mm and 40) often end up with the "Glock bulge" as they simply expand to fill the tapered chamber and feed ramp area. Sometimes the bulge is serious (as is the bulge pictured in this thread). I've seen simlar bulges. 45 ACP models don't seem to be affected as much becasue, again, in my experience, 45 brass is generally VERY strong relative to the pressues involved.

I've experimented with stronger springs, and, as Tuner indicated, springs aren't the issue. The issue in my experience is simply generously cut chambers. If you read this and take issue with it, please measure some Glock chambers (9mm and others) before you make any claims one way or another.

The only cure I've found for the bulge started with a K and ended with an M (middle initial was a K). All joking aside, bulge issues curiously dissappeared when I dropped a KKM barrel in my G29. KKM 10mm chambers ARE NOT tapered.

1911Tuner
January 22, 2006, 07:06 PM
Howdy Gman, and welcome to the fray.

I agree in that I haven't seen the number of bulge/blowout issues with the 9mm Glocks and .45s as with the .40 calibers. Don't see many 10mm pistols around here, so i can't make a call on those. I think that a lot of it is as much due to the powder burn rate in some of the factory ammo, as well as the non-supported head area and/or headspace. Tolerance stacking being the beast that it is...you'll get it with one pistol and not a problem with another, seemingly identical gun. When the powders...or even a single lot of powder...couples with just a weeeeeeee bit too much working headspace,
and just a weeeeeeeee bit too little chamber support all come together,
the results are seen in the photos that started this sparring match.
You can't see the dimensional issues with the eye. It's too small to see...but sometimes it only takes a little. Mass-production being what it is, there are really no two guns alike.

For the record, I don't hate Glocks. I don't like them for my own uses and purposes...but these reasons are largely personal and have no place in a
technical discussion. Glock autopistols for the most part are solid and reliable workhorses...but the Glock fanatics sometimes lose sight of the fact that
they're prone to the same issues that any other mass-produced firearm is.
Sometimes ya just gotta take the sugar along with the....non-sugar.:p

Again, I would strongy advise anyone who experiences bulged cases...no matter who the gun is made by...to have the headspace verified with standard gauges. Don't ignore it! The bulged brass is tryin' to tell you that somethin' is BAD wrong. Eyes and fingers don't regenerate, and it only takes once to book a ride down The Highway of No Return.

Cheers!

jungle
January 22, 2006, 07:08 PM
Thegman, I would agree with that and that is why problems seem to be few with the 9mm and .45 models. It also seems that those who limit themselves to recent production ammo have fewer problems in the .40 and 10mm.
It is my impression that Glock has been making their chambers a little closer to normal with the Generation 3 and later production. Do you find this to be the case?

JohnKSa
January 22, 2006, 07:12 PM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.Enjoyed the lively debate, as always!Same on this end. ;)

If I'm ever going to be in the neighborhood, I just might take you up on the barbecue invitation. I make it a point to never pass up good barbecue.

I'd have ta pass on the turbocoffee--I see right through your flimsy little plot. Get me all hyped up on caffeine and then take me out and embarrass me at the range while I'm so shaky I can't load my own mags... :D

1911Tuner
January 22, 2006, 07:27 PM
John said:

>I'd have ta pass on the turbocoffee--I see right through your flimsy little plot. Get me all hyped up on caffeine and then take me out and embarrass me at the range while I'm so shaky I can't load my own mags.<
********************

Gotta do somethin' even the playin' field with these old tired eyes of mine...I'd rather think of it in terms of what Chief Dan George told Clint Eastwood in The Outlaw Josey Wales:

"Actually I was lookin' to gain an edge."

:D

Thegman
January 23, 2006, 04:37 AM
Thegman, I would agree with that and that is why problems seem to be few with the 9mm and .45 models. It also seems that those who limit themselves to recent production ammo have fewer problems in the .40 and 10mm.
It is my impression that Glock has been making their chambers a little closer to normal with the Generation 3 and later production. Do you find this to be the case?

Hi jungle,

My G20 is a 3rd Gen pistol (about 3 years old at this point) and it's chamber seems to be as loose as any others I've seen (not that it's not shootable, it's no looser than any other Glock 10mm chambers I've seen). I've not examined any Glocks newer than this, but I hope you're correct about tighter chambers; I never liked the "Glock bulge" in my brass.

1911Tuner
January 23, 2006, 06:55 AM
thegman...Does the bulge seem to be ammo-specific? Notice it more frequently or to a greater degree with certain brands?

JohnKSa
January 23, 2006, 11:28 PM
WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

I've been thinking about this and some other things I've read/heard. I believe that anything that gets the brass started deforming will cause it to be temporarily more "plastic" than normal. That would mean that if the headspace is long, or the chamber is too large, that would start the brass stretching/flowing and once it's stretching/flowing, it's going to be less resistant to the pressure than normal.

If all/most of the Glock 10mms have tapered chambers with similar dimensions, but not all/most Glock 10mms bulge brass, then that makes me wonder if the tapered chambers are a major contributor--ditto with the chamber support. I'm leaning toward Tuner's headspace theory as the best explanation.

So, the headspace gets the brass started deforming and makes it more plastic than it normally would be--then the large chamber and support issues allow it to deform even more. On the other hand, if the headspace is ok, then the other two factors aren't enough to cause the bulge alone. Perhaps the same would occur if the chamber was especially large in a particular gun even if the headspace is ok.

That's pure speculation, so I'm not going to defend it rigorously--it's just something that's been knocking around in my head.

1911Tuner
January 24, 2006, 01:22 AM
John said:

>I've been thinking about this and some other things I've read/heard. I believe that anything that gets the brass started deforming will cause it to be temporarily more "plastic" than normal. That would mean that if the headspace is long, or the chamber is too large, that would start the brass stretching/flowing and once it's stretching/flowing, it's going to be less resistant to the pressure than normal.<
********************

Makes sense. As with anything, once it starts moving, it takes less force to keep it moving. Add heat to the equation and...

Gunny------>Makes a note of the theory for future discussion.:cool:

Thegman
January 24, 2006, 02:36 AM
thegman...Does the bulge seem to be ammo-specific? Notice it more frequently or to a greater degree with certain brands?

thegman...Does the bulge seem to be ammo-specific? Notice it more frequently or to a greater degree with certain brands?

Tuner,

I never shot a lot of factory ammo through my 10mm's, but, in general, the hotter the ammo, the more the bulge. e.g. Win. Silvertips bulged a bit more than, say, PMC Starfire, but all bulged to some extent. I should clarify however, the bulge picture in the photo on this thread is extreme, and is not the "standard Glock bulge", nor is it the "Glock bulge" I'm talking about from my stock Glock 10mm barrels. That case is showing an incipient case failure, IMO.

The only time I've seen bulges close to that extent was when I was first developing "real 10mm level" handloads years ago, loads similar to the level that Mike McNett sells through Double Tap. In fact, the bulges were from Blue Dot data Mike had developed himself - this was several years before he started Double Tap. I was using Remington brass that had been reloaded several times, and a few of the top loads looked similar to the brass pictured in this thread (needless to say, I abandoned that load and have gone to 800X for my hottest 10mm loads). Anyway, as I noted earlier, I later switched to a KKM barrel and all bulges dissappeared. Even in my hottest 10mm handloads, which are at the same velocities as Double Tap's 10mm ammo, I don't see bulges like the one pictured in this thread, even when fired though my stock barrels.

atblis
January 24, 2006, 03:05 AM
I found the brass on the ground. It appears to be once fired to me, and are most likely factory loads.

As to the condition of the gun, I know it's a Glock but that's about it.

Didn't Clark play around with a Glock 10mm a bit.

jungle
January 24, 2006, 03:33 AM
On the contrary, thanks for the inspiration for so much fun. Sorry you couldn't participate.

albanian
January 24, 2006, 07:52 PM
I think we have all got a little off the main point here. The point is, if you buy a Glock it has a better chance of blowing up in your face than any other pistol of that price range. If you want a pistol to explode in your face, Glocks are probably for you. If you want a pistol to NOT explode in your face, try something else.:)

Also, I once hear that it only costs Glock about $37 to make a compeat pistol. That is one HELL of a markup my friends! Most other makers spend at least a few hundred dollars on a pistol that retails for $500-700 but not Glock! Talk about not getting much for you money. Look at a SIG and then look at a Glock and tell me that they are about the same quality. I don't think so!

jungle
January 24, 2006, 08:36 PM
If you look around there are documented accounts of almost every type of gun blowing up. Manufacturing defects are a very small subset of blowups, most of them can be traced directly to the user or the ammunition.SIGs are nice, as are H&K, Beretta and many others including Glock. Some look for certain qualities in a handgun that are dependent on usage and individual preference.
Albanian won't be buying a Glock and that's fine. Millions of people are happy with Glock's combination of light weight, corrosion resistance and reliability.
Use what is comfortable and works for you. Going with one of the top makers with a good history of market success is always preferable to getting a second or third grade weapon, even if it means buying used instead of new.

albanian
January 24, 2006, 11:12 PM
"Albanian won't be buying a Glock and that's fine."

I never said that. If I can find a nice G-19 3rd gen I would but that. I have also considered a well used G-17 just because that is the flagship if the Glock line and what they are all judged by. I think if you stick to 9mm and you buy used at a good price, they are good guns. I just won't be buying anymore of the .45s or the .40S&Ws.

jungle
January 25, 2006, 12:03 AM
That's nice. Hard to beat those two.

albanian
January 26, 2006, 02:18 AM
My post talking about the Glocks blowing up was meant to be a joke. I hope people understood that I was at 90% joking on that one.

1911Tuner
January 26, 2006, 08:29 AM
My post talking about the Glocks blowing up was meant to be a joke. I hope people understood that I was at 90% joking on that one.

Most Glock folks don't take jokes about their guns too well, albanian.

Can't figger why they're so touchy unless it's 'cause the things are so gawdawful ugly that they feel like everybody picks on'em.

:evil:

No no! Wait! Hold your fire! It was a joke! I SWEAR it was a JOKE!!!!

KC&97TA
January 26, 2006, 02:37 PM
I had a Glock Model 20, 10mm... had and still miss it, I will buy another one down the road and a model 22 barrel as well to properly shoot the .40 S&W out of it.

The Glock Model 20 is a great gun in my opinion, from the looks and research provided, you need to have a gun smith look at that gun, I never had a single malfunction with my Glock.

I don't know why people get rid of guns like they're a red headed step child, you don't sell your car when it only needs a tune up?

Glocks aren't ugly, they're a finely crafted military weapon, there's nothing pretty about an M16 :neener:

R.H. Lee
January 26, 2006, 02:49 PM
I pick up my first Glock tomorrow. I traded my Springer Milspec for a G21 and I'm already thinking about a buying a G17.

Watch this for awhile. It's mesmerizing. http://www.sniperworld.com/glock/

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