Dominic's Killed Barrel: A Timing Study


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1911Tuner
December 7, 2004, 07:26 AM
Since this one is being watched closely, I decided to start a new thread so that it will be uncluttered. Fairly long, but a good read for students of the
1911's design and function. Pay attention Dave...Ya might just learn somethin.' :p

Dominic! The clearance at the frame bridge being a little less than .020 isn't critical. .010 is good as long as the barrel and slide don't crash.
The gun may be a trifle more sensitive to being kept clean...but you're probably fine on the clearance.

The Scheumann Timing Test has one flaw. It only determines the timing at the END of the sequence, and ignores the beginning. The clearance has to be there at the quarter-inch mark...but it's also important that the
barrel BEGINS linkdown at the right time.

It's often been said that the link's sole function is to unlock the barrel, and that's true enough in a purely technical sense...but it also has another equally important function that it shares with the lower lug's geometry.
It also TIMES the linkdown sequence...and the linkdown must begin and end at the right time. Too short advances it. Too long delays it. Lower lug geometry also figures in, but I'll defer the explanation until a later point in this thread. As little as .003 inch in length can make a very real difference.

The scraped/polished areas that you described suggests...just as a best guess, because I don't have the gun...that the link is still a little too long...
and the lower lug is just a bit out of spec on the forward radius...to allow the sequence to START at the right time. This condition will not correct itself,
and the barrel won't catch up. If it starts late, it ends late. The good news is that since you have enough clearance between the hood and slide bridge...that it probably won't hurt anything.

Slightly delayed linkdown timing isn't an altogether bad thing, as long as the lugs don't crash. The bad thing is...that the window of opportunity is
much narrower. If the gun gets badly fouled, that fouling could
delay the barrel just a tiny bit too long. That's an extreme circumstance though, and you'd likely have to neglect the gun sorely to cause a problem.

Slightly delayed unlock timing allows the use of higher-pressure ammunition without danger of case head blowout because it gives the chamber pressure a tick longer to drop before the sequence starts. I'll provide a link to another thread that illustrates this point. It involved a certain "Officer's Model from Hell" that belonged to forum member "Saltydog" a few weeks ago.

Shoot the pistol as is, and keep a very close watch on the locking lugs...particularly the front one...#3. If you notice even light flanging
on the top of that lug...PM me.

Luck!

Tuner

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hnm201
December 7, 2004, 10:07 AM
Lug#3 is the one closest to the breech, correct?

1911Tuner
December 7, 2004, 10:16 AM
Lug#3 is the one closest to the breech, correct?
________________

Nope...#3 is the one closest to the muzzle. #1 is closest to the breech.
Because the barrel tilts at an angle, #3 has the least clearance because it moves only a small amount compared to #1. By default,
if you've got flanging at #1, you've probably got serious damage at #3.

45auto
December 7, 2004, 11:10 AM
Not to take this off topic, but why 3 lugs in the design?

One or two lugs wouldn't take the pounding?

:)

1911Tuner
December 7, 2004, 11:32 AM
45Auto asked:

One or two lugs wouldn't take the pounding?
_______________

Sure. It could actually "get by" with just one. The Glocks do it.
The #1 lug...the one at the hood...is the anchor for the others. The Big Kahuna. It provides the strength to back up the others. Without it, numbers 2 and 3 wouldn't last long. Face #1 back about an eighth of an inch and go shoot the gun for proof of that. The answer to the next question is...Yes. I have. I've had access to worn out pistols for 40 years. Curiosity and occasional boredom have led to some whacky experiments before tossin' the barrels and slides into the scrap pile.

Now...Would the 1911 be as strong without the forward two lugs? Nope.
They offer extra strength...assuming that they're bearing the thrust load equally...and help to make the gun far stronger than it needs to be to handle the pressures and recoil forces generated by the .45 ACP cartridge. Search for Wild Man Jim Keenan's experiment in which he blocked the barrel with a threaded rod and fired the gun with GI hardball ammo...repeatedly...without damage. Try that with a Glock.

The gun also wouldn't lend itself to the levels of accuracy that it's capable of
were it not for that solid horizontal lockup provided by all three lugs.

Sure...It could get by. But why just get by when you can have somethin' better? :cool:

45auto
December 7, 2004, 11:36 AM
Thanks,

That makes sense. I like "better". :)

Do they still make Glocks? ;)

1911Tuner
December 7, 2004, 04:38 PM
Comin' up on 1600 hours...Wait for it. :cool:

hnm201
December 7, 2004, 10:18 PM
What were we waiting for, Tuner?

I put another 200rds FMJ down range and about 25 Remington Value Pack JHPs. No feed issues, no malfunctions. Pretty smooth, actually.

Re top barrel lugs: #2, middle lug, shows light flanging on the front corners. Lugs #1 and #2 show **no** flanging. :confused:

No battering to the barrel face that I can see.

The feet(toes?) are showing wear on the tips! It looks to me (the uneducated and inexperienced) as if the recoil spring tunnel's areal closest to the bridge has a different shape than what the sistema's barrel's feet were shaped for. Also, as I mentioned before, the feet seem to be slightly compressed, not allowing the link to rotate through them past the vertical lockup position.

Dave Sample
December 8, 2004, 01:32 AM
Well, It Shoots. It doesn't seem to be self destructing like it was, so that is good enough for me. The wear does not surprise me at all and thanks for the Lesson, Tuner. Maybe next time you can teach me somthing I didn't know 50 years ago.

1911Tuner
December 8, 2004, 09:16 AM
Dominic said:

Re top barrel lugs: #2, middle lug, shows light flanging on the front corners. Lugs #1 and #2 show **no** flanging.Okay..You've still got a couple of issues. The good news is that none of them is critical. Your gunsmith didn't do his homework.

Lets break it down and look at the possibilities before we nail the obvious.

Study the barrel in linkdown for a minute. When it's in bed, it's sitting an an angle.

"Light Flanging" is defined as an amount that can't be easily seen, but can be felt with a thumbnail. If you can see it at a glance, it's not light flanging.

Lug #1 has the greatest amount of drop because of the angle of departure from horizontal. It won't get hit unless he barrel is hopelessly out of time.
That was the first "clew" that was evident in your pictures. Lug #3 has the least, and it basically doesn't do much more than rotate.

If #1 is getting hit...#3 is being destroyed. #2 is somewhere between the two extremes.

Your #2 is flanging. There are a couple of possibilities as to the cause...and one true cause. First possibility is that #3 is out of spec short..possibly due to being dressed and shortened on purpose by an armorer long since forgotten. Very likely, but probably not. Second possibility is that #2 is out of spec long...or the slide lug directly in front of it is long. Not likely that this is the case in and of itself, but rather a player with the actual cause.

The most glaringly apparent "clew" is the compressed lug feet...and a point of function on a 1911 that few are aware of.

When the barrel is in full linkdown...the barrel should NOT be stopped by the
bed of the frame, and the barrel's bottom radius should NOT be in dead contact with the bed. The feet should hold the barrel off the bed by a
very tiny amount...about .002 inch...or half the thickness of a sheet of typing paper. Many smiths overlook this when fitting a barrel. They focus their attention on the hood, lockup, and headspacing and ignore the lower lug feet unless there's something obviously wrong. Some aren't even aware of it
and assume that the barrel is supposed to be stopped by the bed.

Some barrels are stopped by the link IN COMPRESSION...but while this is
better than it being stopped by the bed...it's still not correct.

Without being able to examine the gun, I'm gonna say that the feet are holding the barrel off the bed by about twice that amount..or maybe a little more. The barrel doesn't fall far enough to allow lug #2 to get completely out of the way of the slide, and the flanging on the top is the final "clew"
that supports it. In a different frame...the barrel feet may have been perfectly fitted.

To correct this...first confirm that the barrel IS being held off the bed too far
by using strips of paper as a feeler gauges. if this is the case, you need to
tell the smith to reduce the height of the feet slightly. This won't take more than a minute or three. If the check shows that the barrel to frame clearance is good, the lug height will need to be reduced by about .003 inch,
and it may require both operations. If you know how to follow a radius with a file, you can take care of the feet yourself...just be sure to follow the radius
and go slow and use a light touch. Check by holding the barrel down and back semi-firmly with the slidestop pin in place. When the strip of paper is being held tightly enough that you tear the paper before it will slip...you're there. Polish lightly with fine sandpaper to dress the burrs.

Use a good pocketknife to scrape the flanging on the top of the lug and finish by using a strip of emery or crocus cloth to polish it a little with the Chattanooga Shoeshine Boy" method. It doesn't have to be brightly polished...just clean it up a little...and be careful to keep the lug flat across the top. Don't concentrate pressure on the front of the lug. Polish it evenly.

Light flanging indicates a slight problem. As long as the front corners of the lugs aren't being rolled or damaged, the barrel is salvageable. When the lugs are heavily damaged, and the faces are set back the way that yours were...or at least looked to be in the pictures...it's toast. Seen this damage too many times to call it otherwise. Even if the armorer is able to dress the lugs and massage the barrel into time...the shearing damage underneath
the lugs has gone too far, and the barrel should be scrapped or used in a
display pistol only. The barrel will function for a short time, but the lugs usually fail within a couple thousand rounds, and shear off completely. That
catastrophic failure carries the potential to destroy the slide and even the frame.

Cap'n! All due respect sir...but you were whipped before ya started on this one. The Gunn'ry Sergeant requests permission to carry on sir!

hnm201
December 8, 2004, 09:46 AM
On my way into the office, where I will give the barrel a closer inspection.

How does one follow a radius with a file, or learn how to?

1911Tuner
December 8, 2004, 09:58 AM
Dominic asked:

How does one follow a radius with a file, or learn how to?
____________________

Howdy Dominic,


It's easy to do, but hard to describe clearly in print. I will say that it's exactly opposite of how you'd imagine, and opposite of how you might see
the average file jockey do it. If you have a small machine shop in your area,
stop by and ask one of the machinists to demonstrate it. It'll take about
5 seconds to see it as opposed to 500 words to describe it.

If you've still got that killed Nork barrel, I'd like to look at it if you'd be so kind.
Like to check the dimensions and specs on it...

hnm201
December 8, 2004, 10:33 AM
Crikey.

The barrel isn't held off the bed at all. It sits flush in the bed.

:uhoh:

:confused:

1911Tuner
December 8, 2004, 10:51 AM
:D

Don't lose sleep over it. It's not critical, and probably won't cause a problem for a long LONG time...as long as the link isn't being stretched badly as with the frame's impact surface mislocated too far to the rear. Most production guns these days do put the barrel on the frame, and it doesn't seem to hurt anything. The point was made strictly for the purpose of troubleshooting the flanging on lug #2.

Your feet arent restricting barrel linkdown. That's a good thing. The spec issue is with the lug itself. Clean up the flanging...Learn to file to a radius...
and reduce the height of the lug about .003 inch and you'll probably be good to go. Your smith should have caught it...but sometimes time limits cause us to forget...Ask me how I know. :uhoh: :rolleyes:

See? That wasn't so hard... :cool:

hnm201
December 8, 2004, 11:06 AM
So I wonder where the wear on the feet is coming from?

1911Tuner
December 8, 2004, 11:25 AM
Dominic asked:

So I wonder where the wear on the feet is coming from?
_________________

There's the 64-dollar question!

Hard to say. It was a used barrel, so it mighta already been there. If the bottom tips of the feet have small flats on'em...might be that they were filed to address a linkdown problem in another frame. Got pix?

Dave Sample
December 8, 2004, 03:35 PM
OK. These barrels laugh at files and I had to use stones to work on it except for polishing the throat and doing the chamber check notch. I made a post here stating the problems with the Gun and the Barrel. It was installed in a gun that had small dimensions in the slide and the frame relative to the barrel. I offered to clean up the barrel for Dominic and re-link it and that is what I did. I also cut a nice tight bushing for it. There are limits to what you can do with a triple chromed Chinese barrel in a $250.00 1911. If I had the Norinco here with the barrel I could have easily corrected the problems and it would have ran great. No good deed should go unpunished, Right, Tuner? Funny that I get all the Bad Boy Norincos and you get all the great ones. Oh well. Life goes on.

1911Tuner
December 8, 2004, 03:43 PM
LOL. We ain't talkin' about the Norinco barrel no mo'. He's on the
Sistema that his smith installed in the gun

Ya done a good thing. Cap'n, and many thanks for takin' the high road...but that barrel was dead meat before it hit your doorstep, buddy.

Now...I hear tell of another Norinco that belongs to a guy not too far from here that sounds like it's got the same issues. I'm hopin' to get to take a peek and compare it with the specs on Dominic's barrel. If the serial numbers on the guns are close...we mighta identified a bad lot right here on THR.
Ain't that neat?

Dave'n'Tuner...Consumer Protection Watchdawgs.

Got a nice ring to it...dontcha think? :cool:

See? I even let you have top billin'. :D

Dave Sample
December 9, 2004, 06:07 PM
Thanks for the update. I give up again.

1911Tuner
December 9, 2004, 06:43 PM
Quote:

I give up again.

:what: NEVER give UP! 'Bout 12 years ago I waltzed with a dagnab blankety-blank :cuss: Officer's Model :banghead: four times before I hit the sweet spot...I was ready to take a sledge hammer to it when all of a sudden birds started singin' and the clouds parted. I reckon the gun gave up and decided to behave its bad self. :cool:

macavada
December 9, 2004, 06:44 PM
:)

Jammer Six
December 9, 2004, 08:13 PM
I give up again.
:what: NEVER give UP!
I think it's a navy thing.

They have this command "abandon ship", and I think the whole philosophy flows from that. :evil:

macavada
December 9, 2004, 10:04 PM
They have this command "abandon ship", and I think the whole philosophy flows from that.

You ARE evil ... and relentless.

Dave Sample
December 10, 2004, 01:00 AM
When I have no idea of what barrel is being used in what 1911 I have to give up. Besides, I am past caring about this thread.

1911Tuner
December 10, 2004, 10:23 AM
Welp...Looks like this one has run its course. Hope it enlightened a few folks,
but no sense in lettin' it go south.

Cheers all!

1911Tuner
December 10, 2004, 04:09 PM
A few minutes after I slammed the door on this one, Dominic PMed me to tell me that he had an update...so it's open again. As long as we don't start
whoppin' each other again, it can stay open.

Dominic...You have the floor, sir. Post away!

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