View Full Version : 7.62x54R Case rupture. Headspace issue or ammo?

March 1, 2012, 06:55 PM
Attached are a couple of pics of a ruptured 7.62x54R case. This was fired in my 1941 Izhevsk manufactured Mosin Nagant 91/30.
This ammo was "gun show" military surplus stuff, wrapped in paper/twine, like the bundles that come out of the spam cans.
This is the only ruptured case I've had out of maybe 40 rounds through the gun. (30 rounds of milsurp stuff and 10 of mixed Wolf and Privi)
Based on the way it looks, I am leaning towards old crappy ammo, but could it possibly be a headspace issue?
I haven't noticed any signs of problems on other cases, but then again I wasn't going over anything with a fine-toothed comb until I saw this one!

March 1, 2012, 07:33 PM
I've seen a lot of that surplus stuff rupture. Never had or seen any brass cases rupture.

Have the head space checked and get some quality ammo.

March 1, 2012, 07:43 PM
If it were head spacing usualy that shows itself near the rim with ring all the way around the case. That is a shoulder split from weakened case.

Note that ammo is corrosive. You should wash the barrell with soapy water and rinse to elimintate the corrosive salts in the primers. I have seen bores showing signs of rust hours after firing that stuff.

Note it is all I shoot out of my 91-30 it does the job. I just spend an extra few minutes cleaning. Though I have not had any cases split like that on me. I have had a couple of .221 Rem Fireball finaly give out after more firings than I can count.

the rifleer
March 1, 2012, 07:53 PM
Its normal, mine did that quite a bit with bulgarian ammo. Its nothing to worry about.

Edit- don't work about the cracks or buying new ammo, it really doesn't hurt anything. Shoot it to your hearts content, then clean the rifle well.

March 1, 2012, 07:59 PM
Agree with poster #3. That is a shoulder split from a weak case.

March 1, 2012, 08:12 PM
Thanks everyone. I agree it appears to be more of an ammo issue, as there have been no signs near the rims on any of the spent cases... I just wanted to get some more opinions on it. I'll probably invest in a headspace gauge anyway.
Roger that on the cleaning. My Mosin gets cleaned immediately after every range visit (as do all of my firearms!). I sometimes will let my other guns sit at most overnight before cleaning, but the Mosin gets cleaned immediately upon returning home.

March 1, 2012, 10:14 PM
Totally normal for surplus ammo. Just wear safety glasses and you'll be fine.

44 AMP
March 1, 2012, 11:42 PM
Being a rimmed case, the 7.62x54R headspaces on the rim. What this means is that as long as the distance from the bolt face to the back edge of the chamber (through the rim) is within proper tolerances the rifle has "correct" headspace.

You could have a jugged, or grossly oversize chamber but if the rim specs are right, you have proper headspace. There are many military rifles that have "excessive" chambers, except for the critical headspace dimensions. After all, each case only needs to fire once....

However, this does not seem to be the problem with your rifle. The split case is typical of low quality ammo, especially after it has aged a bit. All it means is that particular case had something less than perfect QC during its manufacture. Could have been a flaw in the metal, or in the annealing process. Sometimes, its only a case here and there, sometimes it the majority in a particular batch.

Combloc milsurp ammo is not noted for its high quality control. Toss the case, and clean the rifle. Always, Always ALWAYS wear shooting glasses. Even when shooting the "good stuff".

Mike Irwin
March 2, 2012, 06:48 AM
Yep, not a headspace issue at all.

That's a typical failure for a case that's not been properly annealed.

March 2, 2012, 08:44 AM
I agree with all above.

But, I suggest you invest the twenty-five bucks in a no-go gauge as you already stated, especially if you plan on buying any more Mosin-Nagants.

Checking headspace is the safe way to do things with old milsurps with unknown history and unknown condition. Despite their usually stellar reputation for not having issues, one of two Mosins I recently bought failed a no-go gauge test- and it was a re-arsenaled rifle. I solved the problem by swapping out the bolthead with a bit "thicker" one...

Just my $.02...

March 2, 2012, 10:22 AM
I suggest you invest the twenty-five bucks in a no-go gauge as you already stated, especially if you plan on buying any more Mosin-Nagants.

A field gauge would be a better investment for checking any surplus rifle. Many rifles will fail the no-go test and still pass with a field gauge. These rifles are 60+ years old and many were made with looser tolerances.

James K
March 2, 2012, 01:20 PM
No, that is not a headspace problem. The cause is internal case erosion by the acid in powder that has not been properly washed, usually during speeded up wartime manufacture. It is seen on ammunition from all countries (including the U.S.) and with all case materials.

It may show up on the side, neck or near the base, depending solely on the orientation of the cartridges in long-term storage.

The cause is usually not apparent because the problem is not discovered until the cartridge is fired, at which point its initial orientation has been lost.


March 2, 2012, 07:57 PM
its just the ammo being old and how it was stored. You'll get that on occasion with the cheap surplus ammo. I wouldn't look to much into it. If there was a headspace or other issue with the gun, it would be happening everytime. My advice to you is NEVER buy the ammo that comes in that cheap waxey paper wrapped with that rope, unless you opened the spam can it came in. That paper does absolutely nothing to help protect the ammo so the case deteriorates alot quicker that way.

When i bought my first mosin, i bought a couple of those packs with the gun cause its what they had and had the same thing happen. The cases cracked or got stuck in the chamber so i took it back and bought other stuff that had better packaging and it worked fine. So i stay away from that stuff thats sold individually like that, but if you buy a spam can of it yourself, it will be ok

March 4, 2012, 10:50 AM
A field gauge would be a better investment for checking any surplus rifle. Many rifles will fail the no-go test and still pass with a field gauge. These rifles are 60+ years old and many were made with looser tolerances.

Your point is noted, and many will accept/shoot a rifle that only passes a field gauge. I won't...a field gauge indicates that headspace is marginal, and they're rejected under CMP standards.

Definitely not a good idea if you handload, as I do...

James K
March 4, 2012, 10:00 PM
It doesn't really matter who opens the spam can, or whether the packets are waxey paper, or tied with rope, or who won the Academy Award for best dog handler. The damage to the ammo was done long before the spam can was opened.

Look at the "crack" in the case. That is quite different from a stress crack or the case separation seen with excess headspace, or corrosion from the outside. That case was eaten out from the inside; firing just finished the job of opening it up.


March 13, 2012, 09:49 PM
Thanks for all the input. That particular round came from one of those paper and string wrapped packs I picked up at a gun show. I do have a big spam can of ammo that I have not opened yet. Am hoping it's in better shape.

March 13, 2012, 10:21 PM
My friend and I used to go shooting every weekend and fire atleast 400 rounds each from our M91/30s and his M44. Probably half of the 1950s Yugo ammo we fired had some sort of fracture, crack, or flaw in the casings after being fired. We also noticed that some angry Yugo worker put the primers in because they were very deep, our pins were set perfectly and the next tin we got fired jsut fine, still with a lot of imperfections on the casings after firing.

March 14, 2012, 05:21 AM
As far as mil surp (spam can) ammo goes, try to get the newest production date you can. I've shot a poop ton of the stuff and have seen only a few cases look like that. Now I check the head space or have the seller do it for me. And usually I don't pick the empty case up after I rack the bolt back. If it goes BOOM, and cycles ok I'm good with that. :D

March 14, 2012, 09:45 AM
Well we collect them at the range and put them in ammo cans. Steel scrap I guess if you get the primers out, right? We just cleaned up and didnt want to fill the little trash can with all our brass. OP, did you experiment with new manufactured rounds?

March 14, 2012, 03:39 PM
It doesn't really matter who opens the spam can, or whether the packets are waxey paper, or tied with rope, or who won the Academy Award for best dog handler. The damage to the ammo was done long before the spam can was opened.

Your entitled to your opinion, but i don't completley agree When ammo isn't stored right for a period of time, steel cases getting crappy quick. Im just speaking from personal experience, every pack of ammo i have bought individually from a spam can cracked or just plain didnt work. I have bought numerous unopened spam cans and i have never had any issues with it.

James K
March 15, 2012, 11:04 AM
The spam can prevents air from getting to the ammo and preserves it from rust or corrosion on the outside. But if the powder was not handled right, the corrosion comes from acid inside the cartridge case, and the outside packaging doesn't affect that at all.

On a slightly different subject: At one time, sellers of ammunition used to advertise ammunition with corrosive primers as "non-corroded", hoping the buyer would read that as "non-corrosive". If asked, the seller would say that the ammo was bright and shiny, with no sign of corrosion. But the same would not be true of a rifle barrel after firing his corrosive primed ammunition.


Doug Bowser
March 18, 2012, 12:46 AM
I don't agree that splits like the OP experienced are OK. I have seen chambers burned through splits like these. I would change the brand of ammo and bury the errant ammo.

Also, if ammo is stored in extreme hot and cold conditions, the necks can crack even in a tin container. This is called a season crack and happens because the necks are stretched back and forth over the bullet. I got a 1400 round case of 7.62x25mm Tokarev ammo and they were all cracked when I opened the spam cans.


March 22, 2012, 09:37 PM
I've fired a variety of current factory ammo such as S&B, Privi and Wolf without issue. This ruptured case came from a pack of gun show el cheapo, string-and-paper-wrapped ammo.
I do have a spam cam sitting here unopened... maybe I'll crack it and give it a whirl.

Gator Weiss
March 25, 2012, 09:21 AM
Examine the other cases that you fired for irregularities. These cases can show you signs of a chamber problem, head space problem, chamber erosion, and they can show you signs of brittle case necks, cracks and splits, etc, etc. If there are no irregularities of any kind observed in the other 39 cases you fires, then it was probably a problem confined to that particular casing.

You mentioned paper wrapping and twine. I am hoping that you did not try to shoot preservative / cosmolines out of the bore without cleaning the rifle! Case head pressure can climb enormously and this is not a good idea. I have seen it done by beer guzzling morons at a public gun range (they were ejected) who said they do it all the time. Never try to do that. Always there must be a very clean rifle.

The 7.62x54R is a very good cartridge. That large rim leaves plenty for an extractor to grab hold of and pull out of a dirty chamber. The taper in the case allows for easy chambering and easy extraction in a machinegun or a rifle. It was a well engineered case. It headspaces from the rim. Not from the shoulder. that is something to keep in mind.

Understand this particular case is not always made of very thick stock. Often this case was produced on over-worked and under maintained forming equipment. At times this ammo was produced in the third world by disgruntled political prisoners working for no pay. The density of the case material varies. The material alternates between brass and steel of varying thickness and quality. There will be a massive amount of pressure inside that case when it fires. ANYTHING COULD HAVE HAPPENED.

Your best bet is to examine your other 39 cases and go from there. If you have any of that ammo left, examine it closely before you fire it. Come back here and tell us what you find.

March 25, 2012, 09:41 AM
Opened up a can of Russian and the ammonia smell hit me first.Powder had broke down and ate through the case walls on some of the cartridges.

March 25, 2012, 06:12 PM
Nothing wrong with your rifle. It's the ammo.

Those commies were cheap bastards. They cut corners to extremes on production. The steel in those cases was extruded too far without being annealed, and it developed longitudinal weaknesses. If you closely examine a few dozen unfired rounds out of that spam can, you'll probably find several other rounds with the beginnings of cracks showing. If you closely examine all your fired rounds, you'll probably find several others that have cracked. That is very common. It happens to me all the time. The only noticeable problem from it is that the bolt can be a little sticky on the cracked cases. If it scares you, don't shoot any more steel cased commie surplus ammo.

March 25, 2012, 08:23 PM
yup prob the ammo....you'll notice this with 70 year old turk 8mm mauser ammo too! heck sometimes the case will already be split before you shoot it lol