Are the rounds you have trouble with factory or handloads? HOW are the rounds hanging up? Is it failing to feed, with the bullet nose catching on the breech end of the chamber? Or is it a matter of closing hard when the round is almost chambered? If certain factory rounds are catching as they try to enter the breech end of the chamber, then the shape of the bullet may have something to do with it. You may need to stick with the factory rounds that don't have a problem. If your handloads are having the problem, you may need to switch to a shorter-nosed bullet. What weight bullets are you using? I shoot a 213.5 gr (nominal 210 gr.) in my .44 Magnum Rossi, the same bullet I use in my .44-40 Rossi. If you handload, you may need to trim you brass back a bit, and seat the bullet deeper. A firm roll crimp will keep the bullet from backing into the case, but you will need to have a bullet that has a crimp groove in the right place. Hope this helps.