Mine don't like anything but small primers. I had loaded up about 50 cast bullet rounds and the cases were all large primer pockets. Nine out of ten failed to fire. I was getting good hits but they were off centered. I switched to small primer pockets and every single round fired. I tried using the barrel on another(308) receiver but the hammer wouldn't cock. I looked them over real good, took measurements but couldn't find any difference. My personal opinion about the Rossi 7.62x39 is that it's a handloader's gun. Mine is accurate and enough to meet my expectations, it just won't shoot large primers but stuff it with a cast bullet and 8 grains of Unique and voila. It becomes a shooter.