The other day I mentioned the Walther P99 (man that’s good lookin!) and had asked the question why it had two firing mechanisms, namely the QA and the AS. Well, after doing a little digging I was able to find this.
The Walther P99 QA is a pre-cocked striker fired pistol. The weapon can not be fired unless the striker is pre-cocked, much like a Glock. One unique feature of this system is that the slide does not have to be cycled all the way, but only about 3/8 of an inch to set the striker. Thus, if you carry the pistol with a round in the chamber but do not want it cocked, as there are no manual safeties on the weapon, you only need to move the slide back 3/8 of an inch to make it operable.
The Walther P99 AS is a traditional SA/DA striker fired pistol. The weapon, with a round in the chamber, can be fired in Double Action mode initially. The cycling of the slide will allow the pistol to fire in Single Action mode from that point forward. Once firing in Single Action mode the trigger only needs to be released about half way forward to reset the trigger and fire again.
If I were to purchase a P99, it would definitely be a P99 AS. The AS stands for anti-stress and the meaning is clear. When firing a Double Action pistol, the initial trigger pull is going to be long and heavy. This is going to help you to not accidentally fire a round when you are not ready. Also, since, in SA mode, the trigger resets at half way forward, that means that it also does not catch until half way back. Thus, if the striker is fully cocked, a twitch of the trigger finger will not fire the weapon, unless you fully suppress the trigger.
Clear as mud? That’s what I thought, so I went out and found a video to help me understand.