I had an old Uberti that would bind up. The firing pin cratered the opening in the frame, so that when a round was fired, the primer set back and flowed around this crater. This because the gun lacked a hardened firing pin bushing. Check this by removing the cylinder and running your finger across the standing breech, if should be smooth. If you feel any cratering, or puckering, around the opening, this is your problem. You can correct this by stoning it down very carefully, but this is a continuing problem, due to the shape of the firing pin. If you want to go to the expense, a good 'smith can install a hardened bushing. Look at a Ruger Blackhawk or Vaquero in thsi area to see what I'm talking about.
Also, another, and hopefully your problem, is lead build up in the chambers that prevent your cartridges from seating fully. When fired, they are driven back against the standing breech and do no "relax" as in proper revolver firing. If this be your case, then a scrubbing with a wire brush will remove your problem.
Hope this helps,