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Can someone give me a technical explanation of the difference between a single-action and double-action pistol?

As I understand it, a double-action is when you pull the trigger which cocks the hammer and fires the round, and for single-action is a manual cock of the hammer.

Can someone give me a technical explanation of the difference between a single-action and double-action pistol?

On a double action pistol, pulling the trigger cocks the hammer and drops the hammer. On an SA (single action) pistol, the trigger does not cock the hammer. On a DA/SA, the trigger typically cocks the hammer on the first shot, while subsequent shots are SA (I say typically because you could decock after the first round for another DA shot, or you could have something like an HK USP, which can be carried safely in SA mode on the first round, or decocked in DA mode).

Another type of action is the Glock type action, which uses a striker that exists in a sort of half-cocked state, so that the trigger pull is lighter than DA but longer than SA.

Single action (SA) - requires that the action be cocked. The M1911 is SA and may be carried hammer down but must be cocked prior to fire. The M1911 is intended to be carried cocked-and-locked with the hammer back, a round chambered and the safety on.

Double action (DA) - the trigger will raise the hammer ('cocking') before dropping it. A DA pistol may be carried hammer down and the action will be 'cocked' by the first pull of the trigger. The relatively long/heavy trigger pull of a DA shot militates against them.

SA/DA pistols will function in DA for the first shot and SA for subsequent shots AND after 'de-cocking' (as dropping the hammer without firing is known). SA/DAs may be differentiated by a three position SAFE-FIRE-DECOCK control.

'Revolvers' may be SA or DA. With 'exotic' exceptions they will not be SA/DA.

Self-loaders/'semi-automatics' use excess energy from the previous round to chamber the next round and cock the action/hammer. They may be SA or DA or DA/SA.

My personal weapon, a H&K USPc .40 is SA/DA and I carry it hammer down. As in the Glocks and the H&K P7, modern semi-automatic pistols blur the SA/DA boundaries nicely.

Can someone give me a technical explanation of the difference between a single-action and double-action pistol?

In addition to the other correct descriptions listed, the most interestring difference is a two to four- and- a- half pound trigger pull on a well-tuned single action trigger, as opposed to an 8 to 14-pound pull with the double-action or *trigger-cocking* design. Think of having to lift an M1 Garand rifle with the pull of one finger, for example, for some idea of the feel of the pressure needed to fire the DA, unless the hammer is manually thumbed back first...though some recent DA designs omit the external hammer as a supposed safety *improvement,* resulting in the heavier pull for each and every shot.

-archy-/-

A single action pistol only fires from the cocked position. A Double action pistol will fire from the hammer down position as well as from the cocked position a Double action only (something of a misnomer) fires only from the hammer down position. The reason DAO is something of a misnomer is it only has one action a long relatively hard trigger pull.

Stay well - Stay safe - Stay armed - Yorktown

Note the SA triger. It's a straight back pull, perfect for control during firing. DA trigers have a curve and are kind of creaky to shoot with because the finger has to curl and squeeze all the way through to get the round fired. Shooting a SA only 1911 is superior in design to shoting a DA/SA in SA mode. The SA only trigger is specificaly designed for perfect SA firing, the SA/DA trigger is on the other hand a compromise.

SA only guns are the real ready to fire military no-nonsense offensive attitude gun. They are fast, simpler, more controllable and all compound to more accuracy power yet more comfort too.