Question for Old Fuff regarding DAO

[HammerBite]

I have a problem with double-action-only semi-automatics.

It seems to me that the hammer must follow the slide as it goes back into battery, yet the gun doesn't double. Does the hammer just fall to a half-cock notch, and, if so, doesn't that batter the daylights out of the notch and the sear? I am assuming that the hammer would build up more momentum falling to half-cock than it does falling to full-cock in a single-action gun.

I need someone to explain how these things work and why they don't beat themselves to death.

I'll take answers from anyone, not just Old Fuff.

 

[jonsidneyb]

Firing pin safety pin block might enable again. Just a guess.

 

[Spartacus451]

There is no "half cock" on a DAO gun AFAIK. There is a single notch and that is the whole deal, that notch is used by the sear to cock the hammer and eventually the sear slips out of the notch after the hammer is raised far enough. Why it doesn't batter I don't know, but I imagine the engagement is different then an SA notch as it might not need to be quite as crisp.

 

[Old Fuff]

Various designs are different, but in general the hammer or striker follows the slide down, but not all of the way. The rotating hammer only falls a short distance before it is caught, and the next (D.A.) pull only has to lift it an equally short distance before it is released. The hammer is rotated (or striker retracted) by the trigger bar, wherein a notch on the bar engages a lug on the hammer or striker until the connection is cammed apart at the end of the trigger's stroke. All in all, there isn't any battering between the parts. Internal firing pin blocks are not a factor, because while the slide cycles the trigger is still being held all of the way back.

Unlike in revolvers, the trigger system in pistols doesn't offer any mechanical leverage to help lift/rotate the hammer backwards, and for that reason the trigger pulls tend to feel rougher and heavier. The exception is seen in striker-fired guns such as the Glock and Springfield Armory's XD series. But it could be said that these are not true double action pistols.