At one point, the Boss tells Serena to "always leave one bullet in the chamber, so when you reload you don't have to rack the slide". The gun was a Colt 1911A1, which when the last round is fired has a slide stop which locks the slide open, eliminating the need to "rack the slide". But if you 'shoot it dry' you still have to 'drop the slide to chamber a round from the magazine. Now you have only seven rounds - one in the chamber and six in the mag. If you fire seven from a fully loaded 1911 (one in the chamber and seven in the mag) and reload, you only have to dump the empty mag and insert a full one. The slide does not lock back because you left a round in the chamber. This is the fastest way to get the weapon back into action and, if you need to shoot while reloading, there is a round in the chamber with which to do so. The rule is - load seven + one, shoot seven and reload.