With the load you're shooting, don't expect much growth in case length. I shoot 9 gr. Unique with the same bullet and there just isn't much change. You can probably make the case (no pun intended) that you want to extend casemouth life by taper crimping but .45 Colt brass is not that difficult to obtain. As previously posted, taper crimp is designed to prevent bullets from being pushed into the case. Roll crimp is designed to prevent bullet from coming out of the case. IMO, with revolver ammunition suggest you use the roll crimp just like factory ammunition. Just my dos centavos, YMMV.I am shooting a 255 grain cast bullet in a Ruger .45 Blackhawk at fairly low velocity. I am using 8 gr. Unique. Don't do any formal shooting with it, just plinking. Thought I would not have to be so picky with case length if I taper crimped.