Roll crimps work well. Also a Harkins crimp which is a shell cut down to 2 1/2" and has a shot card placed over the shot and then a regular crimp using the slightly shorter crimped area to seal the card over the shot. The card prevents an open center area on the crimp, the crimp seals the over the shot. In many loads I have enough room to simply shorten the shell and crimp in a normal fashion or substitute a slightly shorter wad to reduce stack height. Like a shorter red AA wad for the regular AA. I had one load tested and the pressure was just slightly higher that original load and it all fit perfectly in a 2 1/2" shell with a normal crimp.
