7.62x39mm small primer brass vs large primer brass strength

[Clark]

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I wanted to test the idea that the small primer brass was stronger.

Preliminary results with 22.5 gr. W296 and Sierra 2310 180 gr .311" bullets, 2.19" OAL, [73kpsi and 2200 fps Quickload]:
RP brass, WSRP: .005" extractor groove expansion, ruined Yugo SKS firing pin
Win brass, CCI200: .008" extractor groove expansion, Albainian SKS ok

I did the Albainian and large primer first, and I think I have an out of control variable with the tighter Yugo chamber drove the pressure up. Here are some pictures of the embossed shape of the brass case head that flowed into the Yugo breech face. Note the embossing aroung the "X" where the brass flowed into the extractor slot of the bolt.

I have more firing pins on order and will try again with shorter OAL.

 

[Clark]

another picture

 

[Clark]

yet another pic

 

[grendelbane]

I learn something new every day. I wasn't aware that 7.62 x 39 was available in both primer sizes.

This appears to be a new trend for a new millennium. 10mm and .40 S&W are kissing cousins, with different size primers. Some of the new .45 green cartridges are loaded with small primers.

I understand the first .357 magnum's were available with large primers back in the '30s. I have the American Rifleman where Elmer Keith first introduced the .357, and he stated that S&W recommended not reloading the .357 brass. His reloads were in .38 Special.

Have I missed any cartridges where some one could have a choice of primer size?

 

[Clark]

Remington does not make 7.62x39 brass anymore. The only small primer SKS base size brass still in production is Lapua 220 Russian, which is VERY costly.

I can get more power out of a 40sw than I can from a 10mm becuase of the primer size, so I went to great lengths to buy old Remington brass with small primer pockets off Ebay. So far, my math says it should work, my 40sw/10mm data says it should work, but my SKS does not agree. I have some out of control varaibles, and I am rebuilding an SKS that got wrecked from this experiment, and I hope to resume soon.

 

[grendelbane]

That happens to me all the time. I hate it when reality conflicts with my theories! :banghead:

I too have noticed many things being dropped from production, and I end up chasing them on E-Bay.

In some ways, E-Bay is a time machine!

Just think of all the stuff you would try and bring back if you had a real time machine!

If I could visit a 60's or 70's gunshop, I would bring back several boxes of Remington .41 mag lead.

I would also try and retrieve my youthful eyesight.

 

[Poodleshooter]

What I don't get is why companies standardized on large rifle primed cases instead of small rifle. The usual powder load for this round is under 30grs of ball powder,so about equal to the .223 Remington. Add to that the shorter length of the short Russian,and it sure wouldn't seem to need a large rifle primer's additional brisance. Plus, I'd imagine that SR primers are marginally cheaper to create.