Whats the deal with 7.62 54r rim size variation

CousinTony

CousinTony

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I picked up some MFS heavy grain and a crate of 147 grain Russian surplus for my SVT 40. It ate up the MFS but the Russian surplus stuff was 'sticky'. I noticed later that the Russian surplus stuff had a slightly wider rim on the cartride than the MFS. It's not much ( maybe 1/64 inch) but if you multiply that by 5 cartridges it's enough to put extra pressure on the rims and makes them dig into the top of the mag as well as the shell below. This makes the odd cartridge stick. I notice it the most when I go to chamber the first round, I pull back the bolt, let it go and it will stick. It doesn't happen very often while shooting.
Theres no doubt that it's the extra rim causing the problems. The rim will leave a gouge mark on the cartridge below as it's being chambered, thats how much things are grabbing. I've also had the magazine follower jam. I think the extra amount of cartridge rim is throwing off the angle of the follower in the mag. It's actually getting better the more of it I put through the gun. I think the top of the mag is wearing down a little and getting polished up. More than anything I was curious why theres the extra rim on the cartridge. I thought maybe it was ammo made for machine guns. I checked out the headstamp info online and says that it's Russian, made in 1975. The cartridges are bronze color, primers are glued in with red glue and the tips of the lead are painted silver.
And it's not a gas adjustment problem. If I try to strip a shell off a loaded clip with my thumb it sticks tight. The rim digs into the shell below hard. I'm not saying that this ammo wasn't made to Russian spec. I just think it's weird that the Russian stuff would be wider when it obviously isn't liked by a Russian gun. Curious if anyone else has noticed this or had similar problems.
Peace.
 
svt-40 mag problems

The SVT-40 magazine was designed to hold 10 rounds of ammunition. With our wonderful gun laws, it was decided to limit these rifles to 5 rounds, so the magazine had to be altered to comply with the law.

I would suspect that your magazine has been pinned or had the internals modified to hold just five cartridges, but with a minimum of depth. Therefore the follower is not going down far enough to hold these particular cartridges, and is "hitting bottom" on the magazine modifications. This puts too much pressure on the follower and spring, and when you jam the fifth cartridge into the magazine, then this minimum measurement does not allow any more compression of the spring.

The solution would be to take the magazine apart if possible, and SLIGHTLY increase the depth of the modification so that you could get these cartridges to work properly. This would entail about 1/8 inch to 1/4 inch more space.

Not knowing how your magazine has been modified or pinned, I can not give you an exact procedure, so you are going to have to do this yourself or have a gunsmith do it if you want to aleviate this problem.

If you have access to another magazine, you might try it to see if these cartridges will work with it.
 
Interesting, I have some 1948 Russian that appears to do the same thing in my Mosin Nagant carbines. I thought the gouge was happening on ejection and I may have a burr in my chamber but now because of the consistency and lenght of the mark and the fact it is identical with 2 rifles it may be happening as the round is chambered. I'll check that next time at the range.
Factory code is 270. I'm sure quality control between the different Russian factories is not one of their strong points.
 
howasan said:
Interesting, I have some 1948 Russian that appears to do the same thing in my Mosin Nagant carbines. I thought the gouge was happening on ejection and I may have a burr in my chamber but now because of the consistency and lenght of the mark and the fact it is identical with 2 rifles it may be happening as the round is chambered. I'll check that next time at the range.
Factory code is 270. I'm sure quality control between the different Russian factories is not one of their strong points.
Click to expand...

This problem was reported during the war when manufacturing variations caused the SVT-40 to be unreliable in combat. Mosin Nagants could supposedly digest the worst of manufacturing differences. It's weird that you are having trouble with the nagants as they should be more forgiving.
 
skirsons said:
This problem was reported during the war when manufacturing variations caused the SVT-40 to be unreliable in combat. Mosin Nagants could supposedly digest the worst of manufacturing differences. It's weird that you are having trouble with the nagants as they should be more forgiving.
Click to expand...

Hey, it's still functioning. They only needed to be 'minute of man'.;)
Fine rifles for sure.
 
buffdog, thats a good thought but its not whats happening. I have two different SVT's. One has a full sized original mag pinned to 5. The other has a original mag chopped down to 5. It happens in both.

howasan, no doubt you've got the same thing happening. My shells all show the gougemark. My factory code is 69, I read online what factory that was but don't remember the name.

skirsons, thats why I asked. I thought someone else must know about this or at least noticed the variation. MFS has a noticeably smaller rim and it runs smooth.
 
arizonaicedtea said:
Just guessing but maybe the MFS has a smaller rim for that exact reason?
Click to expand...

...maybe the reason this ammo is for sale to us here is because the Russians wanted to clear out a warehouse of out of spec, unreliable ammo that wouldn't work right in their guns...:)

I've had similar issues. My snap caps seem to have bigger rims than my S&B commercial ammo.
Perhaps they had a bit of trouble holding spec?

http://www.canadiangunnutz.com/forum/showthread.php?t=561692
 
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Theres alot of guns that take the 7.62 54 cartridge. Including machine guns. I think that SVT's are just fussy. The first problem is trying to feed a semi auto a rimmed cartridge...
 
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