Common Actions on Handguns
Handguns fall into two basic types: revolvers (that fire from a revolving cylinder), and pistols (all other types, including auto-loading and single-shot handguns).
There are two common types of action used in sport shooting.
Single-action means that the gun must be manually cocked for each shot (revolvers) or for the first shot (autoloaders), usually by pulling back the hammer or cycling the slide.
Double-action means that trigger movement cocks the action as the trigger is pulled during firing, but the gun can also be manually cocked like a single action. A gun which can be cocked only by trigger action (no manual cocking) is known by the term double-action-only.
Single-action's manual cocking allows a shorter, lighter trigger pull that is an aid to accuracy; but an accidental light touch of the trigger will usually fire a cocked single-action gun if the safety is off. Double-action's trigger-cocking allows a faster shot, since no separate manual cocking is needed. A double-action gun's longer, heavier trigger pull is also considered safer. In fact, many double-action guns, especially revolvers, have no mechanical safety at all, since only a long, deliberate pull will fire the handgun.