I am working on an Erma RX22, 22lr pistol. The chamber is short. I believe the throat is not quite long enough, and the bullet shoulder is contacting the rifling. I hear European chambering dimensions for 22lr are different then the U.S. has, and this situation is not uncommon on their firearms with U.S. ammo. Some rounds don't quite chamber all the way, and I have misfires. Light hits, as I believe the FP is driving the cartridge all the way in, weakening the blow. The gun often short cycles also. Doesn't always pick up the new round. I believe there is extra resistance to extraction, because of this, siphoning the recoil energy. This is with HS ammo. I had access to a rougher reamer, and it took out a little swarf at the throat. This improved things noticeably, but I am still not there. I think a finish reamer will complete the job. Being this is not a target pistol, going bang is more important to me, than gilt edge accuracy. Which type reamer is most likely to get me where I want to be at?