Does such a cartridge exist? I recognize that most persons using this calibre are shooting steel case stuff in semi auto rifles but a few of us have bolts and reload. Just looking at the 7.62x39 cartridge, it seems to cry out for an improved case, in the same way that a 303 British does. The only problem I can see is perhaps reduced mag capacity in a bolt gun such as the Ruger 77 MII or the CZ (my 303 Epps has a slightly reduced mag capacity due to the fatter case). Any thought from anyone. Thanks.

One thought right off the top of my head without the least research. Say ".300 Savage". If you're lucky. Seems like a lot of trouble for little gain, though I'm thinking you want to stay with the same bore size. Okay, two thoughts. The 7.62x39 already has a short neck and it'll get a bit shorter if you follow the basic Ackley format for improvement.

One version of the Improved 7.62x39 is the 30 PPC

knobmtn

The 7.62x39 imp is a nice looking round, the neck is not at all to short. I played with one in a Competitor handgun awhile back. I honestly dont remember what the vel gain was, being a 14" barrel doesnt tell you what a rifle would do either.
Hiredgun, send me an e-mail and I'll send you the terrible picture I just took of the standard and imp cases side by side. Al Straitiff of Comp. Corp. has the reamers.