we have a package for the vr80 that will allow you to shoot 1 1/8 oz shot @ 1145 fps and includes porting that takes the muzzle rise and torque to the right out, call for info TSS@ 361/241/1091
Slide to frame fit is 2nd to a good barrel fit. Have had several colt 45's that had a loose slide but a match barrel fitted tight and shot great. As long as slide, barrel & sights are all fitted right, it will shoot. The bullet is long gone before slide or anything moves.