FWIW, I've had both break action (Baikal), as well as a bolt action (CZ 527) rifles for the 7.62x39, and both suffered the same hard-extraction problems with various milsurp ammo. Not unusably so, but notably annoying. I suppose you could load your own, but it seems counter-intuitive to load 7.62x39 and shoot it out of a $1000 rifle that gets hung up quite a bit. My 527 in .204 runs smooth and doesn't cost much more to feed than the x39 527 did, once you get a good stash of 1F brass tucked away. A .223 527 would likely be even cheaper to feed. I did my part to experiment with x39, and if I leaned anything, it that it's best suited for an SKS/AK, IMO.