in battery - the firing position
I was taught that the most inportant moment for a revolver's lock-up is when it is "in battery". That instant when the trigger is held to the rear most position, the bolt is engaged in the cylinder notch, & the hand is still holding pressure on the cylinder ratchet.
the litteral meaning of the word "battery", a group of things acting together.
So yes, it is the firing position.
Most revolvers will have a slight cylinder slack when checked with the hammer down & the trigger released. Try your favorite older gun with the trigger held in it's rear most position. If there is not excessive wear in the ratchet, hand area, you will get tight lock-up "in battery" position.
Jim