Originally Posted by SouthernBoyVA
True in regards to the Glock design, false for the M&P as was previously noted. With the M&P, the trigger bar does not complete the cocking of the striker because the striker is held in a fully cocked condition by the sear.
In the M&P, the striker is moved ever so slightly to the rear as the trigger in pressed and the sear rotates. Even if only a negligible amount (1%, 2%, 3%?) that movement makes it a double action as the trigger press completes the cocking process.
Glock and S&W Armorer
Glocks: 17L, 22, 22C, 23, 24C, 27, 34