Nothing wrong with 4.5 in a 1911 but When I use it I have to go to 4.7 to lock the slide back on the last shot. For some reason it ran out of gas. My small group does that ever once in a while but we are on top of the screw up an give the shooter fits. Break out the wood dowel and hammer and if you are shooting a lead bullet you are ready to go. No harm done. If it don't recoil something is wrong. I swelled 1 barrel in 50 years of shooting and it was on a 1911. Leave the 1911 in battery when you whack the bullet with the magazine out or it can screw the slide stop.