Split Casings - Norc 7.62x51 steel cased in M305 Shorty

D

dflight

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Hi Folks,

I've put around 150 - 250 rounds of copper washed surplus chinese 7.62 steel case ammo through my newish shorty M305 over the course of 3 or 4 range sessions. I recover most of my 'brass' to keep the range tidy and it's easy with the roller magnet. I've noticed that about 10-20% of the casings from last two range sessions have had splits in the necks of the cases, on a few these don't start on the mouth but part way down the neck and a couple the split extends down past the shoulder. There is no carbon residue extending further back down the casing and the primers aren't showing excessive pressure signs.

1) Is this an issue for concern?
2) If it is a serious problem, is more likely to stem from the rifle (chamber too large, headspace issues?) or the ammo (weak/poorly annealed steel)?
3) Anyone else have the same issues?
4) Am I being paranoid for asking, or not paranoid enough for continuing to shoot this stuff?

As an aside, my glasses keep getting spattered with oil with every shot. I know that this rifle runs grease not oil, any ideas where the oil (probably original to manufacture & shipping) is hiding and how to remove it?

Any help/advise is greatly appreciated.

Cheers,
-Dflight
 
I'm not concerned with minor splits in steel casings.

The oil is most likely coming out of the rear sight. Disassemble it and clean up the excess.
 
Steel will crack under alot of pressure which is normal. I have not fired steel cased so i can't really say on that point just what i know from working with steel. Just take it to a smith and set your mind at ease then you will know for sure and wont have to worry about something happing with shooting it.
 
Mine split too. Pretty frequently I might add. I've had one or two expand enough that it takes a 2x4 on the charging handle to remove them. I guess thats why its bad to fire that stuff through a higher end bolt action.
 
rodbunlap said:
Mine split too. Pretty frequently I might add. I've had one or two expand enough that it takes a 2x4 on the charging handle to remove them. I guess thats why its bad to fire that stuff through a higher end bolt action.
Click to expand...

That sounds more like an issue with the rifle to me!
 
Do you have a set of verniers or digital calipers? Check out the diameter of the fired cases whether they be brass or steel, against SAAMI 308Winchester max chamber dimensions, not cartridge dimensions,.. noting of course the same measurement locations at the front of body and neck area. You may have a very generous chamber in circumference, if the brass meets or exceeds this SAAMI chamber dimensions after firing and in it's stretched and shrunken position. This situation is hard on cases,and not really a good idea for accuracy in the traditional minded, match-chambered folk's mind,... but then again I read one US M-14 guru who believes this situation where the cartridge is sitting slightly low and below center-line of the bore in a generous chamber, is a repeatable situation that actually lends itself to repeatable accuracy in the M-14 whereby the round will center itself on start of pressure build and even straighten the projectile pointing it parallel and concentric with bore. Who knows, I just plug and play.
 
Use 7.62 NATO specs, not SAAMI .308 Winchester, to check the headspace. These rifles are chambered to the NATO spec, not .308.

Not a single rifle at Hungry's Peace River clinic came anywhere near meeting SAAMI, yet they all shot safely and some of them extremely well.
 
rodbunlap said:
Mine split too. Pretty frequently I might add. I've had one or two expand enough that it takes a 2x4 on the charging handle to remove them. I guess thats why its bad to fire that stuff through a higher end bolt action.
Click to expand...

If it's not tearing the rim of the case it sounds like an extraction/ejection problem rather than ammo. The bolt isn't travelling far enough to the rear to eject the empty and then the bolt jams the expanded case back into the chamber. That's why you have to reef on the charging handle to get it out.
 
Stevo said:
Use 7.62 NATO specs, not SAAMI .308 Winchester, to check the headspace. These rifles are chambered to the NATO spec, not .308.

Not a single rifle at Hungry's Peace River clinic came anywhere near meeting SAAMI, yet they all shot safely and some of them extremely well.
Click to expand...

Steve you are correct on headspace dimensional differences in .308vs762NATO to the tune of around 13thou.

But I was referring to here is for him to check the diameter of his fired brass at the front of the body and the neck for comparisons against the measured points in the drawings for .308Win, which in this regard is the same as 762NATO. The case is allowed to stretch back farther in the NATO chamber I agree, but what fills up the front of the chamber as it fireforms and stays there is approximately the same. I was just trying to show how his chamber size at the front of the body in diameter,.. can cause splitting in steel cases that are not so stretch friendly in the circumference department. Am I making any sense? I can't find NATO chamber dimensions drawings. I know the neck size and body at the front on my nork are quite large, telling me the chamber is generous throughout with ample room to chamber when dirty or even dirty ammo and not just in the headspace dimension.
 
In my fairly plain M14s,

These cases split at the shoulder (and necks, less often) pretty regularly. Not that I care, obviously... but is damage related to gas erosion, anyone know? What if someone got a rifle and fed it an exclusive diet of splitty-case Norincammo? hmmm

...the rifle digests brass with no issues, just so y'all know. I attribute this trend to less ductile case material, and am glad to shoot copiously without worrying about finding the brass later... :dancingbanana:
 
I've had some minor splits at the necks of 7.62 chinese surplus as well. About 1 in 10 maybe, not a hell of alot but it is happening. Headspace was checked and is within reasonable limits when I bought the rifle (Norinco M14/M305, obviously). I have shot about 60 rounds of South African R1M1 ball without any splits in the cases and 40 rounds of .308 MFS without any splits as well. This leads me to believe that its the ammo. Having said that I will continue to shoot this cheaper Chinese 7.62 as the odd split at the neck doesn't worry me too much and the damaged ones are few and far between really, overall that is. Finally I always wear my glasses shooting it anyway, better safe than sorry, and that oil on your glasses is the cosmoline that the rifle is practically dipped in by the Chinese as a anti rust and preservative. It flys around when you shoot and the best way to get rid of it is to disassemble the rifle and wipe it down completely and apply grease where necessary upon re assembly.
 
Mine seem to split below the shoulder and usually split for about a third of the case length. My buddy forgot 308 ammo one day and fired the same steel cased rounds through his bolt action, he had the same results. Split cases on 3 of 10 rounds fired, causing the bolt to be very hard to lift to eject the round. I'd post a picture but I don't have one laying around. They're split and the outside of the case around the split is blackened by powder. I bought it used and was assured that it was headspaced properly but I don't have the exact number laying around.
 
Hi Guys,

Thanks for all of the responses, it looks like this is happening to others as well, with no kabooms yet. I do not (yet) have a set of calipers but as I expect to start reloading (pistols first) I'd best be getting a set. I've shot 290 rounds (I did an inventory last night). I figure on a 3% loss of casings to the grass and weeds, and I've counted 31 recovered casings with splits. Three of those have splits back past the shoulder. The head stamp indicates 1992 ammo. I have some commercial .308win but I'll hold off running that through the rifle until I've measured a few fired 7.62 casings to check chamber size. So far I've not had any issues with extraction - every shot fires, ejects and cycles the next round in so the casings aren't getting stuck.

I peeled the rifle down to major components and wiped the oil off of it when I first got it, but didn't strip the sights down. I guess I have reading to do on that so I can shoot this without install windshield wipers on my glasses. We use a lot of carburetor cleaner at the rental shop, would that be appropriate to use as an oil stripper/degreaser?

Thanks again,
-DF
 
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Hey folks, check this out; (sorry no pix)

Just tidying up, and found on unfired rounds, in the structure of the steel (that is to say, copperplated upon,) some flaws in the shoulder of the case!

They look just like... precracks! Almost exactly the same shape and location as the usual neck and shoulder cracks, just needing a firing to complete the job. ...made during the swaging process?

Thank god it's cheap ammo, hmmm?
 
I'd be interested to know what the dimentions of an unfired case is compared to a fired one. I wonder if a combination of generous chambers and undersized cases could be working together. Or simply undersized, damaged/brittle cases. Sounds like the defects may have come from making the cases not fireing them.

"Kayser Sose", try seperating the ones you suspect have precracks out, then see how many of them crack when fired vs. How many of the rest crack when fired.
 
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