Could this be excessive headspace?


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ldlfh7
June 2, 2014, 02:44 PM
http://i1364.photobucket.com/albums/r735/ldlfh7/mauser/mausershell_zps90601aba.jpg (http://s1364.photobucket.com/user/ldlfh7/media/mauser/mausershell_zps90601aba.jpg.html)[/IMG]

Are the discolored rings at the base of the case the beginning of case head separation? Could this be excessive headspace?
These were all fired out of a Turkish mauser.
I have fired quite a few cartridges out of this rifle but recently began reloading for it so I began paying more attention to the fired brass.

The middle casing is a factory PPU once fired.
The left is a reloaded twice fired PPU.
The right is a reloaded twice fired S&B.

I have never seen this discolored ring at the base of a brass piece before this rifle.
Should this be taken to a gunsmith?

I am not getting any other high pressure signs.

Ideas?

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rcmodel
June 2, 2014, 02:49 PM
No, it is normal expansion.
The part nearer the head is thicker case web and doesn't expand as much as the thinner part further foreword.

http://i81.photobucket.com/albums/j219/rcmodel/-2.jpg

Case head separation will occur farther foreword then that where the brass taper thins out.

rc

ldlfh7
June 2, 2014, 02:59 PM
Thanks a bunch RC.
This is a relief.

LAGS
June 2, 2014, 09:33 PM
You probably dont have excessive headspace.
But what is the harm in having it checked anyway.
I recomend doing it on All Mil Surps, even ones that have matching numbers.
Put it this way,
What does a gunsmith charge to do it for you ?
And how much does your doctor charge, or is a body part worth ?
Not to mention what you paid for the gun.
Better safe than sorry.

rcmodel
June 2, 2014, 09:44 PM
IMO: Excess headspace will net you broken cases with no harm done to you or the rifle.

It was so common for cases to break in military rifles in the old days they issued everyone a broken case extractor so they could get them out and get back to business.

Nowadays, with modern strong brass, it IS a warning sign to Do Something about it.

But it will not shoot your eye out, or blow you up when you start getting them after one firing new brass in an old mil-sup with excess headspace.

It is simply a mild warning sign something is amiss.
And that needs to be addressed post-haste before you continue shooting it.

rc

Jim K
June 2, 2014, 10:40 PM
True, to a point. But very excess headspace can leave the rear of the case protruding from the chamber enough for the case to burst and release high pressure gas into the action. The result can be interesting, but also dangerous, ruining the rifle and injuring the shooter.

The case stretching that indicates excess headspace is pretty unmistakeable. There is a BRIGHT ring of stretched brass 1/4-3/8 inch ahead of the rim. It is bright because it is brass from below the surface that has been exposed as the case stretched; it will show signs of breaking or tearing. Ordinary scratching or wear on the brass from extraction is normal.

Jim

rcmodel
June 2, 2014, 10:46 PM
True that too.

But the OP's cases show no signs of excess headspace, or any case stretch.

That was my only point, before the thread took off into blown-up rifles will tear your head off, and such!

rc

ldlfh7
June 3, 2014, 10:56 AM
So this rifle should not be fired until the headspace is corrected?
About how much should I expect to pay a smith to do this?

Jim K
June 3, 2014, 11:14 AM
I don't think you need do anything. The thread did wander a bit, but everyone seems to agree that your rifle does NOT show signs of excess headspace.

Jim

BBBBill
June 3, 2014, 12:22 PM
As the others said, your rifle does not appear to have excessive headspace. However, checking headspace and other things on a newly purchased gun is routine for me whether the gun is new or used. Only takes a couple minutes and is very easy to do. The peace of mind is worthwhile to me. I do it myself. The gages are not terribly expensive and I the range of calibers that I own is not huge. Some gages work for multiple calibers. When I had a shop I charged $20. For most rifles it only takes a couple minutes to strip the extractor and ejector from the bolt, and insert the gage into the chamber. In you case, the ejector is attached to the left receiver rail, so no need to remove it. Some folks don't remove the extractor, but I do to eliminate any possible influence on the feel when gaging. Should you want to do it yourself, the gages can be rented for $7 plus shipping and insurance. http://www.reamerrentals.com/SearchResults.asp?Cat=47 Just clean the chamber, receiver, and bolt thoroughly to ensure that you're not measuring over dirt and fouling.

Jim Watson
June 3, 2014, 12:54 PM
My question is, what do you do if your cheap surplus rifle demonstrates moderately excess headspace? Enough to show on a gauge but not enough to give casehead separation on cheap surplus ammunition.

In olden days, we blasted away with that cheap surplus ammunition with never a thought as to headspace. Good enough for the army that had issued the piece, good enough for us.

These days, you cannot mention a surplus, inherited, or second hand rifle on the internet without being told that headspace measurement before firing is essential.
The problem is, gunsmiths don't work cheap any more and you cannot have a typical surplus rifle's headspace adjusted within the value of the gun. Nor many commercial rifles' for that matter.

People are not good about followup reports.
I do not recall reading an account of what was done to a surplus rifle found to have excess headspace by current SAAMI specifications. Are there any around?

BBBBill
June 3, 2014, 02:26 PM
As long as the gun is otherwise safe, adjust your dies and reload for that specific chamber dimension. Won't do you any good on factory loads, but milsurp rifle shooters are budget minded who probably reload anyway.

4v50 Gary
June 3, 2014, 04:42 PM
What JimK suggested. I wouldn't do anything.

SlamFire1
June 3, 2014, 07:20 PM
My question is, what do you do if your cheap surplus rifle demonstrates moderately excess headspace? Enough to show on a gauge but not enough to give casehead separation on cheap surplus ammunition.

Assess the shooting risks and decide whether to shoot the thing.

I have been studying this for some time and headspace is not an easy topic to discuss. People have fallacious theories on the cartridge case, many believe that it does not, can not, deform. Their expectations are that it is a strong pressure vessel and how much hangs out of the chamber does not matter. However, these same people have contradictory beliefs when it comes to setting the shoulder back on bottlenecked cases. They do believe that pushing the case shoulder too far back will result in case head separations, and therefore you would think they understand the case is weak, but the contradiction is they don’t believe the case head will burst with excessive case head protrusion.

I have searched on the web for numbers for case head protrusion, but the numbers are not out there. This is the most safety critical issue for headspace, but tables of acceptable case head protrusion are not to be found anywhere. Historically, gunsmiths determined acceptable case head protrusion by taking measurements from factory guns. They took measurements of the barrel shank, the receiver ring, subtracted distances, and then after sticking a chamber headspace gage into the chamber, measuring to the bolt face.

I believe the ignorance of this issue is because this is something we shooters do not have to worry about this. The system was designed so that trained monkeys could drop a metal gage into a chamber, and if the gage was not between Go or NO Go, the monkey was trained to take the firearm to a higher authority for assessment. Basically, if the monkeys use the provided gages, use the parts given them, and follow procedures, the firearm will assembly correctly. Notice that this assumes the parts are properly dimensioned. If the monkey’s start removing material off the back of bolt lugs, remove material from receiver seats, cut the chamber cone wrong, or port that 45 ACP barrel too much, then the parts are no longer within factory tolerances and case heads are sticking out more than they should.

It is rare that a factory messes up head protrusion, but it happens. Back in the mid nineties 40 Caliber Glocks were blowing case heads and you can find threads on this. There was a lot of denial about this too, again from people who believe that cases are strong, so strong that they don't need to be supported by the chamber.

There is a wonderful discussion of the importance of case head protrusion in Vol IV of the Machine Gun by Chinn. These pictures come from the section on blowback. Everyone should read this section, because Chinn does such a good job explaining that controlling case head protrusion is absolutely critical in firearm design. And how it effects the design approach.

Notice that case head design limits the amount of allowable movement of the cartridge case.

http://img.photobucket.com/albums/v479/SlamFire/Reloading/Case%20Lubrication/CaseHeadSupportinBlowback_zps2ee7cced.jpg (http://smg.photobucket.com/user/SlamFire/media/Reloading/Case%20Lubrication/CaseHeadSupportinBlowback_zps2ee7cced.jpg.html)



For this bottlenecked system to work, the cartridge had to be heavily greased. The British Polsten automatic cannon used greased rounds, operated on advanced primer ignition, and used this basic concept.

http://img.photobucket.com/albums/v479/SlamFire/Reloading/Case%20Lubrication/AdvancedPrimerIgnition_zps37be99c9.jpg (http://smg.photobucket.com/user/SlamFire/media/Reloading/Case%20Lubrication/AdvancedPrimerIgnition_zps37be99c9.jpg.html)

Timing and just at what pressures are at unlock are critical to gas mechanisms:

http://img.photobucket.com/albums/v479/SlamFire/Reloading/Case%20Lubrication/Limitofcasemovementgassystemresidualblowback_zpse9573e90.jpg (http://smg.photobucket.com/user/SlamFire/media/Reloading/Case%20Lubrication/Limitofcasemovementgassystemresidualblowback_zpse9573e90.jpg.html)

Belted magnums are the most confusing system out there and everyone will have in time, case head separations with these things. While all factory rifles have correct cartridge head protrusion, but between different manufacturers, the shoulder to base distance all vary. The shoulder to base distance is not controlled as these things headspace off the rim. This results in very short case life, the most common problem is case head separations, especially after the first firing as the factory case shoulder is usually very far from the chamber shoulder of the firearm. For belted magnums I lubricate the heck out of the case. This ensures that the case slides to the bolt face without any sidewall stretch. The case shoulder simply folds out to the chamber shoulder establishing proper base to shoulder headspace without creating necking in the case sidewalls, which would have happened if the case and chamber were dry. After first firing I bump the shoulder back 0.003” and use those special Sinclair cartridge headspace gages. There is an excellent discussion of this at http://www.realguns.com/Commentary/comar46.htm “Extending Cartridge Case Life” . The damnable thing is because base to shoulder is not controlled, the die has to be set up for one particular rifle: two rifles in that cartridge would need two unique sizing dies, or you would have to spend a huge amount of set up time sizing ammo from the other rifle.

The US Army, (Air Corp and land units) and the US Navy used the 20mm Hispano Suiza from WW2 through Vietnam. After WW2 automatic oilers were installed, but during WW2 the automatic cannon used pre-greased cartridges and because of the grease, they got lucky. As Chinn discusses here, the grease saved them!


The Machine Gun, Vol 1 LTC Chinn, 20mm Hispano-Suiza page 589

http://www.milsurps.com/content.php?r=347-The-Machine-Gun-%28by-George-M.-Chinn%29


Thus the most vital measurement (headspace) in any automatic weapon was governed by chance in this instance.

An unfortunate discovery was that chamber errors in the gun could be corrected for the moment covering the ammunition case with a heavy lubricant. If the chamber was oversize, it served as a fluid fit to make up the deficiency and, if unsafe headspace existed that would result in case rupture if ammunition was fired dry, then the lubricant allowed the cartridge case to slip back at the start of pressure build up, to take up the slack between the breech lock and the breech lock key. Had this method of “quick fix” not been possible, the Navy would have long ago recognized the seriousness of the situation. In fact, this inexcusable method of correction was in use so long that it was becoming accepted as a satisfactory solution of a necessary nuisance.

SlamFire1
June 3, 2014, 07:33 PM
Excessive headspace can result in catestrophic firearm failure.

This low number 03 was purchased and disassembled by the winner of this auction. This is the auction description. The receiver seats showed lug set back and that was probably the cause of the rifle blow up as the case head had blown.


http://www.gunbroker.com/Auction/ViewItem.aspx?Item=190985391

This item is a Springfield Armory model 1903 rifle that is a good wall hanger. Its been hanging on the wall of the shop for about 22 years. It is that bad a shape it has been blown up. This is a low ser # of 236162, I had this hanging on the wall to show people what would happen if they shot one of the old low ser # rifles with modern ammo. Look at the pictures to see that this is NOT a shoot able rifle. The guy that shot this rifle spend 4 days in the hospital getting metal out of his eye & metal out of his arms. No FFL required. I will send out a email at the close of the bidding, please copy & send back with payment. I’m selling out a gun shop that was in business for over 30 years. More parts & pieces to come. The shop did a lot of general repair & that’s why all the different parts. This and a bunch more that will be coming up for sale were in 4 other old gun shop’s that I’ve bought out over the last 31 year’s.

http://img.photobucket.com/albums/v479/SlamFire/Blowups/Single%20Heat%20Treat%20On%20Gun%20Broker/pix161243282.jpg

http://img.photobucket.com/albums/v479/SlamFire/Blowups/Single%20Heat%20Treat%20On%20Gun%20Broker/pix432585854.jpg

http://img.photobucket.com/albums/v479/SlamFire/Blowups/Single%20Heat%20Treat%20On%20Gun%20Broker/pix041055134.jpg

http://img.photobucket.com/albums/v479/SlamFire/Blowups/Single%20Heat%20Treat%20On%20Gun%20Broker/pix036894768.jpg

Jim K
June 3, 2014, 08:57 PM
"For belted magnums I lubricate the heck out of the case. This ensures that the case slides to the bolt face without any sidewall stretch."

That may not be a good practice. The case walls gripping the chamber walls will keep the cartridge from moving backward, reducing the rearward pressure on the bolt face. If the cartridge can slide back, pressure on the bolt face is increased and that is not a good result. For that reason, it is generally not a good idea to grease cartridges as a "solution" to problems associated with excess headspace.

True, some auto weapons have been designed that effectively require greased or oiled cartridges (for example, the .276 Pedersen rifle needed waxed cartridges to function) but there are presumably advantages to the system that outweigh the disadvantages of oiled, greased, or waxed cartridges.

Jim

SlamFire1
June 3, 2014, 10:26 PM
That may not be a good practice. The case walls gripping the chamber walls will keep the cartridge from moving backward, reducing the rearward pressure on the bolt face. If the cartridge can slide back, pressure on the bolt face is increased and that is not a good result. For that reason, it is generally not a good idea to grease cartridges as a "solution" to problems associated with excess headspace.

Jim: Firearms are designed to hold the full thrust of the cartridge, ignoring any and all case friction. As long as you don’t exceed SAAMI pressure specs, the bolt will hold the load for the full service life of the action. The only adverse consequence for what I am doing could be peening, if the headspace between cartridge and chamber is too great, but I have never seen it.

There are people who believe that the case is a load carrying member. They did not come up with this idea on their own, this was something they were taught. It all came about from the early 1900’s problems with the single heat treat 03 Springfields and the subsequent Army coverup of these problems. The 03 Springfield was properly designed to carry the full thrust of the cartridge case, but the single heat treat Springfields were improperly built. The Army built over 1 million structurally deficient rifles, kept them in service, issued them as loaners in rifle matches, sold them to Civilians, and whenever rifles blew up, blamed the blowups on the shooters. To give logic to this cover up, the Army created this theory that the case carries load and removes load from the bolt face. There was actually a method to this, at the time bullets were made from cupronickel and they fouled something awful. You have to shoot cupronickel bullets to understand just how fast and how severely these bullets foul a barrel. Shooters quickly found that a grease coating on the bullet eliminated the fouling.


http://img.photobucket.com/albums/v479/SlamFire/Reloading/Case%20Lubrication/MobileandNevernickelgreasePJOHare_zps089a5ecd.jpg (http://smg.photobucket.com/user/SlamFire/media/Reloading/Case%20Lubrication/MobileandNevernickelgreasePJOHare_zps089a5ecd.jpg.html)

Instead of acknowledging that their defective rifles were at fault, the Army told people that grease in the chamber removed the friction between case and chamber (which is true) and thus, dangerously, increased bolt thrust, which is the lie, sort of. In a properly designed rifle firing ammunition within pressure specs, there is no problem with greased or oiled cases, but in a defectively designed or defectively built rifle, any bolt thrust is a problem. Using this theory the Army was able to scapegoat shooters and misdirect the problem they created. The authority of the US Ordnance Department is so high that no one has ever questioned the basic unstated premise in this theory: that anyone would so stupidly design a rifle to break at a load less than the full thrust of the cartridge. There are generations of Americans who faithfully adhere to the idea that the case is supposed to carry load, and because of the reprinting of Hatcher’s Notebook, future generations will also believe this, such is their faith in the infallibility and inerrancy of the US Army Ordnance Department. In fact, even today, whenever any problem happens with an Army weapon, the first thing the Army looks for is an oil can to blame.

The 1921 coverup of the problems of the tin can ammunition would have fizzled long ago except for the multiple reprinting of Hatcher’s Notebook. Reconcile Hatcher’s 1947 account of the 1921 Tin Can ammunition fiasco and all the warnings about “increased bolt thrust” and this, which Hatcher wrote in 1933. Do bolt guns and semi auto’s operate in an entirely different physical world, following different set of physical laws?

Army Ordnance Magazine, March-April 1933

Automatic Firearms, Mechanical Principles used in the various types, by J. S. Hatcher. Chief Smalls Arms Division Washington DC.

Retarded Blow-back Mechanism………………………..

There is one queer thing, however, that is common to almost all blow-back and retarded blow-back guns, and that is that there is a tendency to rupture the cartridges unless they are lubricated. This is because the moment the explosion occurs the thin front end of the cartridge case swells up from the internal pressure and tightly grips the walls of the chamber. Cartridge cases are made with a strong solid brass head a thick wall near the rear end, but the wall tapers in thickness until the front end is quiet thin so that it will expand under pressure of the explosion and seal the chamber against the escape of gas to the rear. When the gun is fired the thin front section expands as intended and tightly grips the walls of the chamber, while the thick rear portion does not expand enough to produce serious friction. The same pressure that operates to expand the walls of the case laterally, also pushes back with the force of fifty thousand pounds to the square inch on the head of the cartridge, and the whole cartridge being made of elastic brass stretches to the rear and , in effect, give the breech block a sharp blow with starts it backward. The front end of the cartridge being tightly held by the friction against the walls of the chamber, and the rear end being free to move back in this manner under the internal pressure, either one of two things will happen. In the first case, the breech block and the head of the cartridge may continue to move back, tearing the cartridge in two and leaving the front end tightly stuck in the chamber; or, if the breech block is sufficiently retarded so that it does not allow a very violent backward motion, the result may simply be that the breech block moves back a short distance and the jerk of the extractor on the cartridge case stops it, and the gun will not operate.

However this difficultly can be overcome entirely by lubricating the cartridges in some way. In the Schwarzlose machine gun there is a little pump installed in the mechanism which squirts a single drop of oil into the chamber each time the breech block goes back. In the Thompson Auto-rifle there are oil-soaked pads in the magazine which contains the cartridges. In the Pedersen semiautomatic rifle the lubrication is taken care of by coating the cartridges with a light film of wax.

Blish Principle….There is no doubt that this mechanism can be made to operate as described, provided the cartridge are lubricated, …. That this type of mechanism actually opens while there is still considerable pressure in the cartridge case is evident from the fact that the gun does not operate satisfactorily unless the cartridges are lubricated.

Thompson Sub-Machine Gun: … Owing to the low pressure involved in the pistol cartridge, it is not necessary to lubricate the case.

fguffey
June 4, 2014, 03:02 PM
True, to a point. But very excess headspace can leave the rear of the case protruding from the chamber enough for the case to burst and release high pressure gas into the action. The result can be interesting, but also dangerous, ruining the rifle and injuring the shooter.


"For belted magnums I lubricate the heck out of the case. This ensures that the case slides to the bolt face without any sidewall stretch."

It had to happen, not to me, this stuff does not drive me to the curb. I am not a slide and glide shooter. I want nothing between my case and the chamber but air, not a lot of air but I want clean air. I know, the case is embeddable, particles between the case and chamber will embed into the case, problem, embedded particles will cause skid marks, I have ask the question "Has anyone seen-found skid marks on the case and or chamber?" , the answer is no or no answer. I want 100% contact. nothing holds like 100%.

There is no substitute for learning to reload, reloading includes case forming, fire forming is a matter of chambering a round and pulling the trigger just to see what will happen. A reloading fire former should learn to measure before firing, after firing and again after sizing. It would help if the studied the incline plane. Threads are incline planes/

http://www.edinformatics.com/math_science/simple_machines/screw.htm

There must be something that happens to some when the bolt closes, for me the chamber does not get dark, the lights do not go out.

I am the fan of cutting down on all that case travel, if the case is not long enough I get a longer case. Case head protrusion and unsupported case head, I measure.

This low number 03 was purchased and disassembled by the winner of this auction. This is the auction description. The receiver seats showed lug set back and that was probably the cause of the rifle blow up as the case head had blown.

was probably the cause The case head failed, the case did not have case head separation, I purchases cases that were suspect, before I was advised the case heads 'COULD' fail I fired 40 of them twice, not a problem but, the cases became collectable so I moved them to the collectable drawer. I was disappointed, after tumbling and loading the cases were magnificent looking cases.

F. Guffey

Jim K
June 4, 2014, 03:23 PM
Hmmm. One expert genius advocates greasing cases and another expert genius says not to do it. Not to mention conspiracy theories. And all that for the price of admission. Where are the dancing girls?

Jim

SlamFire1
June 4, 2014, 04:17 PM
If all you can do is rely on authority, because you don’t have the education or smarts to understand firearms design, then the world is a very confusing place. All these divergent opinions.

In so far as greased rounds, they are a historical fact, go argue with the Navy manual below. The Hispano-Oerlikon was a blow back cannon, used by the Navy from WW2 all the way through Vietnam. One reference states that 150,000 of the things were made and were in service during WW2. The WW2 era cannons required greased ammunition, post war an automatic oiler was added, to function or it would rip the case in half.


You can see at exactly 2:14 on this WW2 video a Sailor’s hand painting grease on the 20 mm ammunition loading machine for the Oerlikon anti aircraft machine guns.

http://www.youtube.com/watch_popup?v=9dR3h2HdnBQ


Figure from The Machine Gun Vol V Hispano-Oerlikon page 358

http://www.milsurps.com/content.php?r=347-The-Machine-Gun-%28by-George-M.-Chinn%29


http://img.photobucket.com/albums/v479/SlamFire/Reloading/Case%20Lubrication/Hispano-OerlikonMachineGunVol5page358_zps75046bd9.png (http://smg.photobucket.com/user/SlamFire/media/Reloading/Case%20Lubrication/Hispano-OerlikonMachineGunVol5page358_zps75046bd9.png.html)


There were problems if the grease film was inadequate:

http://hnsa.org/doc/gun20mm/part4.htm


ORDNANCE PAMPHLET NO. 911 March 1943


GREASING AMMUNITION

All 20 mm. A.A. Mark 2 and Mark 4 ammunition MUST BE COMPLETELY COVERED WITH A LIGHT COAT OF MINERAL GREASE BEFORE BEING LOADED INTO THE MAGAZINE.

The ammunition is usually packed greased. However, this grease tends to dry off. Whether cartridges are packed greased or not, they should be regreased before loading the magazine.


NOTE-A small amount of mineral grease, applied shortly before firing, to the cartridge case that is visible in the magazine mouthpiece, will assist in preventing a jam in the gun barrel.

Dry ammunition or ammunition with insufficient grease will jam in the gun chamber when fired and extraction will be very difficult, if not impossible. See Page 110 for use of torn cartridge extractor.

fguffey
June 4, 2014, 04:52 PM
Are the discolored rings at the base of the case the beginning of case head separation?

I have ask the question "Has anyone seen-found skid marks on the case and or chamber?" , the answer is no or no answer. I want 100% contact. nothing holds like 100%.

I am the fan of cutting down on all that case travel, if the case is not long enough I get a longer case. Case head protrusion and unsupported case head, I measure.


ldlfh7, Your cases are normal, you do not have a ring, to read the case understand the case was supported by the chamber when fired. The part of the case you are worried about was not supported, that is the reason for the dull finish. There is a difference between unsupported case head and case head protrusion. Of all my rifles the maximum amount of case head protrusion is .120", one more time unsupported case head is greater than case head protrusion. I measure. I measure case head thickness from the bottom of the cup above the web to the head of the case. I have domestic case heads that are .260" thick, I have surplus case heads that are .200" thick.

It should not take anyone long to determine the .350" thick case head is safer if there4 was a problem with case head protrusion. Problem. No one ever considers the amount of pressure required to crush the case head to the point it would become unsupported. I have crushed case heads when testing suspect receivers but not to the point I created a case head failure, remembering the case head must not be hard, it could split.

Remerging the case head crushes and increases in diameter with normal factor loads, normal? A close guess would be .00025.

F. Guffey

ldlfh7
June 4, 2014, 05:30 PM
Everyone -

Thank you for the education.
This is why I really enjoy this site. Good information and education on problems otherwise tough/impossible to determine by myself.

Thanks again!

Jim Watson
June 4, 2014, 05:49 PM
The despicable Hatcher says the case protrusion from the chamber of a 1903 is .147 to .1485". No doubt assuming in-spec barrel and cartridge.
I once read somewhere that a '98 Mauser was .110".
Are these gunsmith measurements, design specifications, or scaled/calculated off a drawing not showing case support/protrusion as a basic dimension? I don't know, but they are what we have.
The redoubtable Guffey reports a maximum in his rifles of .120" by measurement. He also finds case heads .200"+ thick, so that there should not be any thin case wall trying to contain chamber pressure.

However, the case head IS containing chamber pressure, look at Chinn A in post #14.
Pressure is not exerted exclusively straight out against the chamber walls and back against the bolt; it is exerted equally in all directions. You can draw a line from the cartridge interior to open air passing only through the brass of the case head. Pressure is exerted along that line just as much as in any other direction. Therefore the brass must be thick and hard enough to hold the pressure. It is not just a gasket. If the case were fully supported and serving only as a gasket in all areas, we could still be shooting folded head cartridges.

SlamFire1
June 4, 2014, 08:41 PM
The despicable Hatcher says the case protrusion from the chamber of a 1903 is .147 to .1485". No doubt assuming in-spec barrel and cartridge.
I once read somewhere that a '98 Mauser was .110".

Otteson took measurements off existing specimens and must have had the same sources as well, which would have been Hatcher. This post summarized Stuart’s measurements:

http://www.practicalmachinist.com/vb/gunsmithing/sako-extractor-rem-700-bolt-194240/
OK, finaly got to my copies of Otteson vol 1 & 2 lastnight, and lost the first copy of this post this morning.

The following are Otteson’s figures for how much a case head protrudes out of the breech end of the barrel with the bolt locked.

Ottesson reckoned on typical mass production clearances between the top of a bolt rim and the breech face of a barrel being around 10 thou, and diametrical clearence between the bolt nose and barrel counterbore of a Rem 700 being around 10 thou. And a simillar 10 thou diametrical clearence between the walls of the bolt head counterbore and the case rim and head. Because of difficulty achieving concentricity in the investment cast Ruger 77, it has a 30 thou diametrical clearance between case head and bolt face rim.

He cautions that a re barrelling a rem 700 to a closer fit makes the rifle much more sensitive to dirt, like unburned powder grains or stray cleaning brush bristles.

Case Head Protrusions after Otteson
Action______________Protrusion (inches)
M98_______________0.105”
03 Springfld_______ __0.147 to 0.148
700 Rem____________0.160 plus any chamber mouth radius
Sako 461 (Vixen) _____0.107 annular ring around breech face of bbl for extr nose clearence
Win mod 70 (post 64)__0.125
Weatherby Mk V_______0.13”
Savage 110__________Pre ’66 (rem type extr) 0.144”--- Post 66 win mod 70 type extr 0.128”
Ruger 77_____________0.132” (push feed – controlled feed may be less – I really don’t know)
Carl Gustav
(Dovetail shaped lugs)___0.120
Browning BBR_________0.160 (0.13 counterbore, +0.015 clearence + chamfer)

US Patent numbers:
Sako type extr 431,670 (Paul Mauser)
Win mod 70 / savage 110 type extr 431,669 (Paul mauser)
Rem 700 breech 2,585,195 M H Walker Apparently with v good description of tests.

The Mauser 98 sets the standard, as the thin extractor allows very deep seating, however this is achieved at the cost of cutting down the bolt rim for most of its circumference, and leaving a great gaping hole in the receiver inner collar for the extractor to go through.From the base of the case head to the thin web is around 0.10”, (I have a sectioned 30-06 somewhere but I am not going to measure it) if the allowable distance up the case is 0.005” to 0.015” before it bursts, that is a small distance and one that allows very little of the case head to be unsupported.

However, the case head IS containing chamber pressure, look at Chinn A in post #14.

Yes, just the case head. Pressures inside the barrel are also in the yield range of the case material. The entire cartridge is not a strong pressure vessel, the weakest part of the case bursts around 650 to 750 psia. Removal of the bolt at pressure will result in the case head being blown out of the chamber because the sidewalls are not strong enough to hold the entire case together.

Pressure is not exerted exclusively straight out against the chamber walls and back against the bolt; it is exerted equally in all directions. You can draw a line from the cartridge interior to open air passing only through the brass of the case head. Pressure is exerted along that line just as much as in any other direction. Therefore the brass must be thick and hard enough to hold the pressure. It is not just a gasket. If the case were fully supported and serving only as a gasket in all areas, we could still be shooting folded head cartridges.

There is no doubt that once smokeless powders came in, and pressures rose from the blackpowder 5,000 to 20,000 psia (or so) case heads had to be made thicker. I know you are aware that old blackpowder guns had barrels of wrought iron, a material that would not hold up to the pressures of smokeless.

In so far as the case not being a gasket, this reads as an debate over terms. And truthfully, I don’t know where something stops being a “gasket” and is considered something else. I am aware of guys who double gasketed their cylinder heads, because it was too much work to remove the engine block for decking. It did not work for them, the double gasket blew. If the case was “fully” supported we would need to use a ram rod to eject the fired cases as there would be no room for an extractor.

The despicable Hatcher

In so far as Hatcher being despicable, the path of life for successful men is complicated; messy. Hatcher wants to sell books, yes, and wants to have a long and lucrative career after retirement. After having climbed to the top of the Ordnance Department, which is a remarkable achievement, he is either working for the American Rifleman, or applying for a job there. When he finally dies in the early 60’s he has made it to the top job at the NRA, the head of the executive committee. Hatcher is an extraordinary individual of enormous talent and ability. But, he owes himself everything, he owes us nothing. Remember that, he owes us nothing. His career is of his own making; he spent an enormous amount of time, effort, becoming a pre WW2 celebrity, becoming a contributing writer through a number of publications, writing books that have been standard reference books, etc. He had to be an outstanding manager of men, material, and organizations. A most remarkable man. After retirement, he is not going to ruin his good relationship with the Army by pointing out any of their mistakes. He does not owe us that, he does not owe us anything. Hatcher misdirects any Ordnance Department mistakes away from the Army. In his writings the Army always appears in the light it thinks of itself: wise, all wise, warrior gods, totally superior to all the minions out there, perfect in all regards, and nothing is its fault.

Hatcher was a success. He managed to achieve tremendous things, his career path was better and farther than 99.999999% of the people out there. Not everyone has enough organizational maturity to understand that he had conflicts of interest, nor do they see how he resolved them. It is remarkable how many stay under his spell almost 50 years after his death never questioning anything he wrote.

Jim K
June 5, 2014, 12:33 AM
"If all you can do is rely on authority, because you don’t have the education or smarts to understand firearms design, then the world is a very confusing place. All these divergent opinions."

I was considering a reply to the nastiness and arrogance contained in that statement, but decided that it would be pointless in the face of such absolute knowledge of one's superiority to ordinary humans who dare to have "divergent opinions."

Jim

fguffey
June 5, 2014, 06:48 AM
I have no ideal where Hatcher got the .147" case head protrusion, I have never found an 03 with more protrusion than the Mauser. The only part of the case head that protrudes .090" is on the side of the extractor, meaning the rest of the case head has less protrusion.

Jim Watson, ldlfh7. thank you, ldlfh7 for my part you are welcome.

F. Guffey

Jim Watson
June 5, 2014, 10:04 AM
I think the German innovation of the rimless cartridge to simplify box magazine design is at fault. A rimmed cartridge need have no protrusion other than the thickness of the rim, backed up by the solid case head, except at the extractor cut. My Remington 788 .30-30 headspaces the rim against the flat breech face and the flat bolt face holds it there. The extractor cut is .15" wide and maybe .050" deep. I think a US Krag is the same, although limited by its single locking lug.

As I cited in the previous thread, Neidner had it figured out long ago. The Mann - Neidner "Hamburg" rifle had interrupted thread locking lugs, screwing the bolt right up to the casehead with no clearance at all. Mann said the rifle would stand overloads that would bulge the barrel and not even blow the primer due to the firing pin design.

I referred to the "despicable Hatcher" because I do not recall having seen Slamfire1 say a good word about him until now.

fguffey
June 5, 2014, 11:44 AM
I am guilty of that, a very boring conversation, for me, starts when some one starts with "Hatcher said" It is not as much about what Hatcher said but someone telling me what he said.

From the beginning the length of the chamber from the shoulder to the bolt face could have been tracked, in thousandths, Springfield nor Hatcher noticed. The third 'exposed' safety lug in front of the rear receiver ring made it possible. All I have ever used on the 03 when checking the length of the chamber from the datum/shoulder to the bolt face is the feeler gage.

I had rather check the length of the chamber from the shoulder to the bolt face with the ammo I am shooting than a head space gage. I have no problem correlating all the measurements.

F. Guffey

SlamFire1
June 5, 2014, 05:01 PM
"If all you can do is rely on authority, because you don’t have the education or smarts to understand firearms design, then the world is a very confusing place. All these divergent opinions."

I was considering a reply to the nastiness and arrogance contained in that statement, but decided that it would be pointless in the face of such absolute knowledge of one's superiority to ordinary humans who dare to have "divergent opinions."

Buck up buckaroo, why don’t you prove to this "genius expert" your vast knowledge on bolt design?

So do something easy, what is the design load for a 30-06 bolt?.

I will make it even easier: given that the 30-06 has a case head diameter of 0.470”, that comes out to a surface area of 0.1735 square inches. I am using the OD of the case, you are free to pick any dimension you want, just tell us why. Anyway, I am going to pick the MAP of 60 Kpsia, though it might be a better choice to use the MPLM or MPSM, what do you think?, which will give a bolt face load of 10, 410 lbs. This load is based on the assumption that the case carries no load, something that apparently, you disagree with.

To plumb this further, I will make it real simple: Just how much load are you assuming the case carries and thus by how much do we weaken the locking mechanism? Let’s make it even more basic, will the case carry 50% of the load, 40%, 30%, 20%,etc, etc?, thus we reduce the bolt structure by 50%, 40%, 30%, 20%, etc, and what is your rationale for that number?

I am not going to ask your opinion on what safety factors to use and I am not going to require a Von Mises analysis, I am of the opinion that early bolt lugs thickness were at best based on maximum shear theory.

Once you give your “opinion” we can call out all the "dancing girls" and strike up the band!!

Jim K
June 5, 2014, 09:48 PM
Your use of the OD of the case head shows a common mistake in talking about pressure on the breech face. The correct way to calculate pressure on the breech face (bolt head) is by calculating the area of the rear INTERIOR of the case, (using trig to figure out how much of the curved interior area is the "rear"). The result in area is then divided into the MAP to obtain the absolute pressure on the rear interior, which is then calculated for the area of the case head. If desired, that can then be converted to PSI for the bolt face load.

OK, return questions. I agree that you seem to be very knowledgeable about some aspects of firearms design. How many firearms have you designed? How many design teams have you been on? How many of your designs have been put into production by firearms manufacturers? I once suggested to Gene Stoner that channeling waste gas back through the bolt was not a good idea; he responded by asking how many military rifles I had designed. A good reply question and it left me more than a bit red in the face. But it didn't answer my question or explain why he had used that system.

Jim

SlamFire1
June 6, 2014, 01:16 PM
Your use of the OD of the case head shows a common mistake in talking about pressure on the breech face. The correct way to calculate pressure on the breech face (bolt head) is by calculating the area of the rear INTERIOR of the case, (using trig to figure out how much of the curved interior area is the "rear"). The result in area is then divided into the MAP to obtain the absolute pressure on the rear interior, which is then calculated for the area of the case head. If desired, that can then be converted to PSI for the bolt face load.

Thank you for a polite and well considered reply.

I disagree with using ID. That was a convention by at least one design bureau and I don’t know why they used it considering they had the ability to actually measure case head thrust. I have examined measured bolt thrust data from a 2010 Army report. The Army “heavily” lubricated 5.56 cases and measured the actual cartridge thrust. The actual, not theoretical case thrust, was higher than the thrust based on ID, and less, than a calculation based on OD. I am of the opinion the lesser value must be due to frictional losses in the lube.Given that the actual case thrust values were above the ID and closer to the OD, I am of the opinion that OD represents a worst case and therefore is the appropriate value to use.

I took several measurements after sawing off a 223 case just above the case head. Sidewall taper just at the case head gives a number of different values, which are different from the ID just above the taper.

http://img.photobucket.com/albums/v479/SlamFire/Reloading/Case%20Lubrication/223Caseheadinternalmeasurements_zpsad8a14ce.jpg (http://smg.photobucket.com/user/SlamFire/media/Reloading/Case%20Lubrication/223Caseheadinternalmeasurements_zpsad8a14ce.jpg.html)

But, your calculation method was used by some, the firearms designed by that method have had excellent service lives, probably due to the safety factors used in sizing the lugs.

OK, return questions. I agree that you seem to be very knowledgeable about some aspects of firearms design. How many firearms have you designed? How many design teams have you been on? How many of your designs have been put into production by firearms manufacturers? I once suggested to Gene Stoner that channeling waste gas back through the bolt was not a good idea; he responded by asking how many military rifles I had designed. A good reply question and it left me more than a bit red in the face. But it didn't answer my question or explain why he had used that system.

His reply was an insulting misdirection: of course blowing waste gas through the bolt was not the best idea, but, based on a Guns Magazine from the 50’s, he did it to avoid paying patent royalties. I am certain he was insulting you instead of providing a serious reply because he knew that DI made for a maintenance heavy and dirty weapon. Issues he would have been reminded of many times in his attempt to sell his weapon system to the Army. As it is, while semi auto DI’s are excellent target weapons, DI is so dirty, the only active general purpose military weapon using DI is used by the US Army, and those countries who accept US weapons as foreign aid. No other front line design, no country which designed a weapon from the ground up, and is using it, uses DI, which ought to show that DI was not the best choice for a military weapon. The number of DI designs out of inventory are greater than the number of DI designs in active duty.

There are features of Stoner’s design I like, I think considering the shoe string development budget he had, he did well. Most of the problems with his AR design could have been worked out had the rifle under gone full scale development, but it did not. Instead good Americans had to die in battle and hundred’s of millions spent fixing what could be fixed given that an immature weapon design was base lined in form, fit, and function. Two problems that remain to this day are the DI system and the magazines.

I have one active firearm designer I talk to, planning to buy some guns off him, one of his designs is in production, and unlike Stoner, he is still alive. He was the bolt designer and he used OD. As an active target competitor, it is surprising all the people you meet, and one, whom I have kept in contact with, was an artillery designer. He told me the typical safety factors he used and he used OD in his designs.

And none of them weakened their design by assuming the case took some of the load.

Jim K
June 6, 2014, 11:24 PM
Sorry, but I do want to clarify something I said. Gene's reply was not intended as an insult or taken as one. He was a good guy and he was joking. I accepted it that way, even with chagrin, something I did not make clear in my post.

FWIW, I have long considered the AR-18/180 to be a much better rifle than the AR-15, and I think had it been ready in time it would have been selected as the M16 rather than the earlier rifle. It would have been more reliable, less fussy, and much cheaper to manufacture. (I would have made the buttstock connection a lot stronger, though.) But the political demand was to get something out there to counter the AK-47 and the AR-15 was all there was.

I considered the vaunted Stoner 63, though, as "simplifying" things in a very complicated way. It was a "tour de force" that wasn't needed, though it impressed the heck out of some generals with that "push-pull-click" stuff. But an army just issues rifles to some and machineguns to others - they don't need to be convertible or combinations.

As for the ID-OD issue, I am not sure which is "correct", and suspect that neither is, since what is involved is relative pressures, not necessarily absolute. The folks who write that cartridge X and bullet Y give 52,286.745 pounds per square inch are not in the real world. I once wrote that there can easily be 100 fps +/- variation in a box of factory cartridges and was taken to task by some guy who read the tables in the Gun Digest and believed the numbers.

I think the whole thing we can say for certain about things like cartridge pressure, is that there are few pat answers. Things just happen too fast and any variations (like the position of the powder in the case resulting from fast feed or slow feed) can change things drastically.

I once did a firing time line in milliseconds and there is not a lot of that "slow push" we read about going on. Bolt lugs get slammed back fast, no matter what the design is.

Jim

SlamFire1
June 7, 2014, 07:12 PM
As for the ID-OD issue, I am not sure which is "correct", and suspect that neither is, since what is involved is relative pressures, not necessarily absolute.

It used to be a designer took the highest number, even though it is only reached for a millisecond, and that became the design load. With the advent of computer models, deflections can be modeled in real time, and that might affect the analysis.

The folks who write that cartridge X and bullet Y give 52,286.745 pounds per square inch are not in the real world. I once wrote that there can easily be 100 fps +/- variation in a box of factory cartridges and was taken to task by some guy who read the tables in the Gun Digest and believed the numbers.

Agree about pressures not being a point value: when I found actual pressure data, the spread is much more than we have ever been lead to believe in the popular gun press. An excellent read on this can be found at http://kwk.us/pressures.html.

Based on this, and basic statistics, given a standard deviation, the frequency of a high pressure shot is surprizingly high.

Page 1-9 AMCP 706-110 on page 1-9 gives pressure data, which is either taken from the 30-06 or the 308 Win. The book gives the example of a 50,000 psia cartridge with a std deviation 5,000 psia. I have seen pressure tested data on the 308 National Match ammunition, with the 168 match bullets, and the limited tests showed 1719 psia standard deviations, so I consider a 5,000 psia standard deviation reasonable over a large lot.

Based on this standard deviation:

15.9 % cartridge have pressures above 55,000 psia

2.3% have pressures above 60, 000 psia (about 2 in every one hundred rounds!)

1.2 % will have pressures above 65,000 psia. (about 1 in every one hundred rounds!)

So I believe the short hand calculation that SAAMI uses for Maximum Extreme Variation (MEV) to be quite reasonable. From http://kwk.us/pressures.html

Maximum Extreme Variation (MEV). There is a small chance that in a very large lot of ammunition, a single sample might test much higher than the averages. From statistics, SAAMI recommends an MEV no more than 20.6% above the MAP.

338 Win Mag 1.206 X 65, 000 = 78, 390 lbs/ in ²

It can be seen that at least once or twice in every 100 rounds, you can expect an 78,000 psia shot with 338 Win Mag factory ammunition!.

Just imagine the extreme high spreads on some people's reloads! Might be some 90,000 psia rounds going down the tube on the rare occasion.

When people raise the bolt loading flag, which they often do, I believe my best advice for that concern is to "cut your loads". Nothing increases bolt loading faster than a couple of extra grains of powder. Believing that case friction is a panacea for high pressures (Ackley anyone?) is about as realistic as believing you can survive a 100 mph car accident, because you put a pillow between your chest and the steering wheel.

I once did a firing time line in milliseconds and there is not a lot of that "slow push" we read about going on. Bolt lugs get slammed back fast, no matter what the design is.

Agree, I think Chinn calls it an impact load. Based on discussions with a number of people, treating the load as an impact load has greatly changed my view of heat treatments, and the great importance of looking at Charpy impact test data.

FWIW, I have long considered the AR-18/180 to be a much better rifle than the AR-15, and I think had it been ready in time it would have been selected as the M16 rather than the earlier rifle. It would have been more reliable, less fussy, and much cheaper to manufacture. (I would have made the buttstock connection a lot stronger, though.) But the political demand was to get something out there to counter the AK-47 and the AR-15 was all there was.

Once something is type classified, goes in to mass production, is issued, it gets very hard to replace. The logistics cost simply overwhelm all other considerations and the political will was not there to force the issue, as there was on replacing the M14 with the M16. Maybe once burnt, twice shy? I have handled an original AR180, looked like a better mouse trap to me, but, “good is the enemy of better”. Currently the military is requiring any replacement candidate to the M4 to be 200% better. I don’t know if there is anything using current materials, technology that will ever be 200% better. These sort of standards cannot be met unless Captain Kirk beams down a couple of phaser rifles for evaluation.

I considered the vaunted Stoner 63, though, as "simplifying" things in a very complicated way. It was a "tour de force" that wasn't needed, though it impressed the heck out of some generals with that "push-pull-click" stuff. But an army just issues rifles to some and machineguns to others - they don't need to be convertible or combinations.

The early M16 had a slamfire problem: primer sensitivity was not specified and exactly what accidents happened, not in any record, but the military reduced firing pin weight and went to a less sensitive primer: the #41. The M16 firing mechanism was not altered as there was enough energy margin to fire the less sensitive primer even down to -40 F. (or -40 C) But, Stoner's 63 version had misfires with the #41 primer!, he must have changed something.

fguffey
June 11, 2014, 03:14 PM
Based on this standard deviation:

15.9 % cartridge have pressures above 55,000 psia

2.3% have pressures above 60, 000 psia (about 2 in every one hundred rounds!)

1.2 % will have pressures above 65,000 psia. (about 1 in every one hundred rounds!)

So I believe the short hand calculation that SAAMI uses for Maximum Extreme Variation (MEV) to be quite reasonable. From http://kwk.us/pressures.html


It can be seen that at least once or twice in every 100 rounds, you can expect an 78,000 psia shot with 338 Win Mag factory ammunition!.



And the spread of pressures had no noticeable impact on the case head thickness and or diameter. When I find case head upset caused by high pressure I do not fined 1 case out of 20 or one case head out of 100 fired cases with upset case heads. I do find cases in groups as in 10 our of 10 or 20 out of 20 cases that were returned to the original box after firing.

F. Guffey

gamestalker
June 18, 2014, 02:26 PM
Even if it did have a head space problem, and it doesn't appear to, if it's doesn't have a serious head space issue, it can often be managed very well after the brass has been fire formed, by not bumping the shoulders back more than necessary when resizing.

GS

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