By a Single Action?
In a Single-Action, When the Trigger Is Pulled, the Hammer Is Released, Causing the Cartridge in the Chamber to Fire. They Are Called “Single Action” Because...
In a single-action, when the trigger is pulled, the hammer is released, causing the cartridge in the chamber to fire. They are called “single action” because only one mechanism – the release of the hammer – occurs when the trigger is pulled in order for the gun to fire.
What is meant by single-action?
So it's easy to understand that in regards to revolvers, single-action means that one trigger pull equals one fired round, and that's it. The shooter then has to cock the hammer to be able to fire the next round. ... The benefit of a single-action firearm is that the trigger pull is both light and short.
Is a revolver single or double-action?
Most modern revolvers are "traditional double-action", which means they may operate either in single-action or self-cocking mode. The accepted meaning of "double-action" has, confusingly, come to be the same as "self-cocking", so modern revolvers that cannot be pre-cocked are called "double-action-only".