Split case diagnostic

[DASHMAN77]

hello. I have recently built a Mosin Nagant rifle. I acquired a Russian Mosin M44, made in 1944, that had been stripped of everything except the sights. All I was given was a barreled receiver (barrel and receiver are both date stamped 1944 and bear the same factory mark) and stock. Being that almost all Mosin parts are interchangeable, I scavenged everything I needed off a Russian 91/30 that I had recently purchased at my work. I loaded 4 Russian steel case, silver tip, 148 gr rounds, stamped 10 (factory made) 71 (production year). Each round was inspected after firing. The first two fired had no visible failures. The third round split vertically just above the neck to the tip of the shoulder. The fourth round again had no problems. I know very little about head spacing and what could cause this to happen. Military weapons are notorious for having the bolts swapped between guns without having problems. I do not have GO or NO GO gauges for this caliber ( 7.62x54R for those who don't know). I was thinking of loading some more rounds, one at a time, in the same orientation ( the 10 on the case situated at the top each time it's loaded and fired, for example) and seeing if this split happens on the same spot. If the split happens in the same spot, what would that tell me. I was wondering too if this type of failure isn't uncommon in steel case ammo that is over 40 years old. Or if this is a common issue with this caliber or this particular make/model rifle. Besides gauges, is there another way to check head spacing or is this unrelated to a head spacing issue? Any help or input would be greatly appreciated. Thank you.

 

[denton]

The Mosin headspaces on the rim.

If the chamber is a little long, you'll get splits like that, but no gas back in your face. It's not the best thing for the chamber, though.

In my experience, brass cases for the Mosin do not come from the factory well annealed. Annealing plus neck sizing often solves the problem. Of course, that means you'll need brass cased ammo.

 

[macgrumpy]

It has nothing to do with headspace, steel case ammo is well known for experiencing vertical cracks like this.

 

[Ks5shooter]

^^^^^^ I agree, especially with older steel ammo.

 

[entropy]

Surplus ammo does that a lot. Inspect your surplus before you load. Splits like that are not uncommon, and the worst result I have had is a little gas in the face. Albanian seems to be the worst for them, but it has happened with just about every type of surplus I've shot, except Czech White Tip (training ammo) Never had a split with that.

 

[BuckleSyxx]

Yeah, steel ammo. When I had my Mosin, it would do this quite frequently.

 

[243winxb]

if this split happens on the same spot. If the split happens in the same spot, what would that tell me.

The round is not being supported by the chamber. Chamber is on the very large size, worn, is my guess.

There are 1000s of these in the scrap bucket at my club. Never noticed a split neck, when recycling. I may need to look harder or get new glasses.

 

[denton]

In modern rimless cartridges, chamber length has everything to do with headspace. In the Mosin headspace and chamber length have nothing to do with each other. The Mosin headspaces on the rim of the cartridge, and, as 243winxb has said, the round is not necessarily supported by the chamber. If the chamber is a little long or a little large in diameter, there is nothing to adequately contain the expansion of the case and it will split lengthwise. Steel is less ductile than brass, and will generally split more often.

I've had the experience of simultaneously having a Finnish M39 and a Russian M44. Out of the same lot of ammunition, the M44 split cases about half the time, and the M39 hardly at all. Also, brass cases from the M44 got cute little pleats on the shoulder when FL resized, indicating poor annealing and excess chamber length. Since the ammunition was from the same lot, and the two rifles produced different results, it follows that the difference in outcome was something to do with the guns and not the ammunition.

Using only brass cased reloads, neck sized and properly annealed, completely solved the splitting problem.

 

[macgrumpy]

While an over-sized or worn out chamber can cause cracks like these the odds are that the problem is the steel case itself, especially older military cartridges. The fact is that all rifles have to have clearance between the case and the chamber so that the case can expand and then contract as it cools. If the case/chamber fit were tighter initially then the case would be difficult to chamber and the bolt would close very hard, what's more, after firing the case would stick to the chamber.

All metals build internal strains when it's moved. Moved metal is any metal that has had a stress or force applied to it and those forces create stains or deformations in the metal. Brass can be stressed more than steel because brass will recover it's original shape more easily (it's more ductile) and as a result it doesn't build large internal strain forces (it's more malleable). Steel on the other hand is less ductile and malleable so it builds large internal strain forces when it's deformed and those internal strain forces cause the metal to harden and crack, that's just the way steel works and it's why brass is the preferred cartridge case material. Unfortunately brass is several times more expensive than steel and less common. The Russians were forced to develop steel cases because of their military needs and their lack of copper resources so they did a good job a making steel work to the best of it's ability to be used for small arms but steel is and never will be as versatile as copper for this purpose.

In the end, yes, the chamber could be worn but even if it isn't older Soviet block ammo will always demonstrate cracking, it's just the nature of the beast. The best chance you will have for not getting any cracking will be if the chamber is new and your cartridges are modern Wolf or Tula ammo, but even then you will eventually see cracked cases.

 

[ford8nr]

So were these reloaded steel cases or did you pull the bullets re weigh the powder and reseat the bullets. Any sizing done in the process ?

Or did I read that wrong and you "loaded" 4 factory rounds into the rifle ?

 

[carbine85]

I think I would mold and measure the chamber. I would also check the head space.
There's only 2 reasons why the case will split:
1) Too much space for the case to expand into.
2) Poor steel used in the case.
I have (5) Mosins and non of them split surplus ammo.

 

[entropy]

I think I would mold and measure the chamber. I would also check the head space.

The first is a waste of time & money. The second should be done before a surplus rifle is shot.

#2 is the reason the case heads split on surplus 7.62x54R.

 

[carbine85]

The first is a waste of time & money. The second should be done before a surplus rifle is shot.

#2 is the reason the case heads split on surplus 7.62x54R.

How is it a waste of time and money? Has anyone properly inspected his chamber? I wouldn't assume anything.

 

[entropy]

If he had fired brass cased commercial ammo and it did that, I'd be the first one calling for a chamber cast. But I collect Mosin Nagants, and am a gunsmith, and have yet to see an M44 that had a dangerously oversized chamber. Or an M91/30, or M91 for that matter. I've seen M91's that had shot out/corroded out bores, but the chambers were not oversized. Steel cased ammo (as well as some brass cased surplus [Albanian]) splits on the neck commonly enough not to be alarmed about it, unless other symptoms are present. I have Cerro-Safe, but I don't do a cast unless I have reason; a couple surplus cases spitting isn't reason enough. ( I do visually check chambers and headspace check before firing.)

 

[Swampman]

I wouldn't worry too much about a small percentage of neck/shoulder splits with old steel cased ammo.

Sometimes stuff just happens.


These neck/shoulder splits all happened on the same day.

The cases were all from Winchester 64 grain Power Point factory ammunition, not reloads.

I can't remember how many rounds were fired that day, but probably @2000 out of 20+ different M4's. Over half the rounds fired were Remington 55 gr. FMJ and not one of them split, so it's unlikely the problem was caused by a weapon with excessive headspace.

I haven't noticed excessive numbers of neck/shoulder splits in Winchester .223 since then. Maybe someone at the brass factory just had a bad day.

 

[GAF]

I once owned a Mosin Nagant carbine (last year made in Russia) that looked like it was new, never fired.
I had split cases like the one the OP is showing all the time with surplus ammo. A friend of my had the same problem
in his older Mosin. I never had the split case problem with modern brass or steel case ammo.
I stopped using surplus ammo.