"Machine gun 308 brass"

[celtgun]

Is brass that has been fired in military machine guns usable after full length resizing? Have read that NM(National Match) and LR(Long range) head stamps are more desierable since they are fired in rifles.
Also does any have experiaence with brass from HK91, sure has a heavy "flute mark". Can it be reloaded?
Thanx in advance. Good shooting to all.

Pray and Shoot Daily.
Lee Jones(Celtgun)


Duty is the sublimest word in our language, Do your duty in all things, you cannot do more; you should never wish to do less.....Robert E Lee

 

[Mike Irwin]

"Is brass that has been fired in military machine guns usable after full length resizing?"

Yes. It's brass like any other.

You will have to do something about the crimping around the primer pocket, designed to keep the primer in place during feeding through automatic weapons, either swaging or reaming the primer pocket.


"HK91, sure has a heavy "flute mark". Can it be reloaded?"

Again, yes. Those flute markings are more cosmetic than they are physical.

 

[kraigwy]

Yes its usable, I've loaded thousands of rounds using '60 brass.

You have to understand that in shooting in ANY auto or semi gun, brass gets stretched more, between the shoulder and rim.

What happens is as the bullet moves down the barrel, it passes a gas port where the gas is bled off to work the action. This starts before the bullet exits the barrel, meaning that the gas starts pushing the op rod back, trying to eject the case while gas is still pushing the bullet, the pressure of this gas is still expanding, pushing forward at the shoulder of the case, and the op rod is causing the bolt to start pulling on the rim, the brass is quite hot at this point so is easily stretched.

This action is more severe in machine guns, meaning the brass is stretched a bit more then on semi auto guns.

This does not mean that the brass cannot be used, it just means more care should be used in re-sizing the brass.

No one should load any brass from any semi or full auto gun without using a Case gage, Wilson, Dillon, RCBs etc. They are used to measure the finished or resized case to make sure the sizing die is set up to size the brass back to specks, mainly in the shoulder to base area. Depending on the gun the brass was fired in the more effort needed to size the brass.

If you can find one, read Gen Hatcher's book MACHINE GUNS, 1916 for a thorough understanding of automatic actions and their effect on brass.

 

[Slamfire]

This action is more severe in machine guns, meaning the brass is stretched a bit more then on semi auto guns

Absolutely true and great post.

Machine gun brass is risky. Chambers on machine guns are often huge and long. You have this thing that is going to get hot as heck, ammunition feeds in at a high rate, the mechanism has massive breech blocks to crunch cases in, and chamber dimensions are huge to maximumize function reliablity. Machine guns are well known to stretch cases.

The typical max stretch of a case is .006". Much more than that and the case head comes off. If you get your brass cheap don't complain if you have early case head separations.

Take a look at this web page, http://riflemansjournal.blogspot.com/2010/05/reloading-case-head-separations.html great pictures on what happens when cases get stretched.

 

[Ozzieman]

SLAMFIRE thank you for sharing that with us!!
I have heard before that if you run a sharp dental pick down the inside of a case you can feel the stretch line like they showed in the article but never believed it until I saw those great photos.
I have some 308 cases I am going to try that with. I had a separation on one of about 150 cases that I got with a gun. I stopped using them.
Think I will pull the bullets on the 25+I have loaded and try that.

 

[chuckhammer]

LC brass has less internal capacity due to its thicker walls for increased durability. As others mentioned, the primers are crimped in place and must either be swaged or turned out.

MG brass is not any worse than M14 brass in my experience.

 

[44 AMP]

What happens is as the bullet moves down the barrel, it passes a gas port where the gas is bled off to work the action. This starts before the bullet exits the barrel, meaning that the gas starts pushing the op rod back, trying to eject the case while gas is still pushing the bullet, the pressure of this gas is still expanding, pushing forward at the shoulder of the case, and the op rod is causing the bolt to start pulling on the rim, the brass is quite hot at this point so is easily stretched.

This action is more severe in machine guns, meaning the brass is stretched a bit more then on semi auto guns.

Pretty good explantion but not 100% accurate. Every system is built with a mechanical delay designed in, so that the bolt does not start moving before the bullet has left the barrel, and pressure drops, allowing the brass case to release its grip on the chamber walls, allowing extraction. However there is still a considerable amount of residual pressure in the chamber and that may account for a bit of the stretching as the case is extracted.

But I think the most probable cause is the chamber dimensions, with machine guns being the worst in that regard. Look at the .303 British. Even when fired from a bolt action, the "generous" chamber allows a lot of case stretch, and brass life is short.

The military simply does not use guns built to maximize case life. That isn't even a blip on their priority radar.

GI brass is heavier and thicker than commercial brass, to ensure it survives the rough treatment of GI weapons, long enough to funtcion. Which it does, by and large. And because it is built "tougher" it usually lasts long enough for us to reload, and usually many times, if treated right.

 

[Slamfire]

All semi automatics are designed to open when the residual pressure is below the rupture strength of the cartridge. Chin in his book said below 650 psia for a 20 mm case. Unlock starts before pressure drops to 650 psia , the correct time displacement curves are in the US Rifle M14 book.

These curves are from AMCP 706-260.

As you can see the residual pressure was measured, that is the little inset in the pressure diagram.

Because the case is extracted under pressure, the front end is still sticking to the front of the chamber. And that is why cases get stretched.

 

[SwampYankee]

I have gotten case head separation a few dozen times with my Enfields. It's pretty much a given, especially with S&B ammo. But I have yet to experience it with my FR-8, MAS 49/56 or FN PBR (which are all .308's). Even when the whole darn backend separates from a .303, I have never had an issue from a safety standpoint. I assume that a .308 bolt action will be OK with case head separation? Am I wrong? What happens if a semi-auto blows a case?

 

[Slamfire]

I assume that a .308 bolt action will be OK with case head separation? Am I wrong? What happens if a semi-auto blows a case?

Cartridge cases act as a gas seal. If the chamber design provides a lot of support, then it is likely the edges of separated case head won't be exposed.

Some semi auto designs, like the Garand, provide good case support. Some bolt gun designs, like the SAKO finnbear, have a lot of unsupported case head.

If the edges are not supported and the combustion gas is free to flow, what happens afterward all depends on the action.

Garand designed his action so the gases go out the top and down the magazine well. The receiver heel is tight to the stock, but he put gaps on either side of the receiver heel as gas vents. This action was designed to protect the shooter in the event of a gas leak.

The 03 Springfiield provides almost no shooter protection. Gas will flow down the receiver rails and firing pin right into the shooters eyes.

Good post war designs like the Savage M110 provide gas baffles and ways to keep gas away from the shooter.

 

[jmorris]

You sure can, most of what mine eats has been reloads (of reloads). Annealing helps out a lot though.

 

[zfk55]

PE 57s and HKs...... This is response of my father's email archives.
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David, the problem you're having is a common one with the 57s and H&Ks. Both have fluted chambers.

The chamber fluting that allows for the blowback cycling is the culprit. Note the longitudinal striations on your expended cases. The brass has bulged into the fluting and you can feel the ridges with your fingers. With a k31 chamber the expansion of the brass is a relatively overall expansion. Not so with your 57. Besides the immediate overall, the expansion is also into the fluting with their sharp edges. This stresses the brass unlike any other chamber. (Except the H&K 91, 21 and 93 and AMT)

Resizing this brass is not only an overall, but inclusive of the bulged striations as well. Bcause of the fluting edges, these striations immediately become the stress points in the brass. Its like bending a piece of thin brass back and fort along a crease. It soon weakens and simply breaks at that point.
If you're determined to resize this brass, do it once and once only. You may not easliy see the minute stress crack (or multiple cracks!), but its not uncommon for a case with unseen interior cracks to open up along more than one longitudinal plane, thus releasing an inordinate amount of gas from the sides of the case all at once. The 57s here proved that point long ago.
Be careful, David. Particularly with softer brass such as Norma 7.5x55. I advise that you stick with new GP11 or at least RUAG match brass which is a bit tougher than most, but whatever you do please understand that annealing will be of little and dubious value with expended 57 and H&K cases.

Be careful.

P

 

[jmorris]

The chamber fluting that allows for the blowback cycling is the culprit. Note the longitudinal striations on your expended cases. The brass has bulged into the fluting and you can feel the ridges with your fingers. With a k31 chamber the expansion of the brass is a relatively overall expansion. Not so with your 57. Besides the immediate overall, the expansion is also into the fluting with their sharp edges. This stresses the brass unlike any other chamber.

That's not that big of a deal either, I have reloaded a lot of brass from 91 and CETME fluted chambers just fine.

 

[Pedersoli]

I've reloded a lot of military machine gun fired 308 brass (some of it several times)

It is a pain the first time. Some of them were .030 over max length, and the primer pockets are a pain with the crimp.

You can get it a lot cheaper though and it holds up well in the long run.

I buy mine from Apex Brass on gunbroker.com for around $150 for 1000 pieces.

 

[swmike]

I've reloaded numerous pieces of "machine gun brass" and have only one real gripe. It doesn't hold enough of most powders to get full velocity with bullets over 150 gr. As a precaution, I anneal all military brass that might have been shot in a Machine Gun so I have no issues with full length sizing.

I got a bunch for free (over 1k rounds) and use it for my 155gr loads (.308).

 

[Ideal Tool]

Handloading Machine gun brass

Slamfire you are spot-on. The late Phill Sharpe covered this topic pretty thoroughly in his Complete Guide To Handloading. Machine guns are pretty hard on brass. This book, even though dated should be required reading for everyone interested in handloading. If they did, 90% of the questions that are being asked in these forums would be answered.