*Most kinds of .45 have unexceptional muzzle energy and are big and fat, giving fairly poor performance even against light, flexible body armour. It was the standard US military pistol round for a long time and many diehards still swear by it, but people who carry guns for a living - cops, soldiers, criminals - are mostly using other calibres these days. (Some spec-ops troops still use .45, as the bullet is subsonic and thus can be effectively silenced.)