Having shot a friend's PCC, I think the stovepipe issue has to do with the stiff recoil spring and heavy bolt. The bolt doesn't blowback far enough, it travels back far enough to pick up a fresh round, but it catches the empty brass as the bolt travels forward. I was shooting 90-95% powder, target loads. Try full power loads, or heavy bullets (124 grain instead of 115 grain), even +P loads if you can find them, so the bolt travels all the way back, until your PCC is broken in. This theory is supported by the fact that the bolt doesn't lock open on the last shot.