The Luger, like the 1911, P.38, Beretta 92, etc., is a locked breech, recoil operated pistol. The recoil operation is usually termed "short recoil", unlike a Browning A5 shotgun or a Frommer Stop, which are "long recoil".
What this means is that the barrel and breechblock are locked together in battery. When the bullet begins to move forward, the barrel-breechblock unit begins to move back. In the Luger, they remain locked together until the knobs strike the sloped surface of the grip piece, kicking the toggle upward and unlocking it from the barrel extension. Momemtum carries the breechblock the rest of the way to its fully rearward position, and the "bounce" off the grip piece plus the energy stored in the recoil spring returns it to battery, picking up a fresh round from the magazine on the way.
In spite of misunderstandings, it is recoil, not gas pressure itself, that operates all these guns. If the bullet does not move, the gun does not function.
The Luger always had problems. It is very accurate, poor sights notwithstanding, but has always had a problem in power balance and in closing power. It is not a tolerant gun and operates well only in a fairly narrow range of bullet momentum (velocity x mass). Closing has been a problem from day one; the shape and angle of the grip are not the work of a human engineering genius as most think, but Luger's desperate attempt to get more downward leverage in a spring arrangement that was more inclined to push forward.
I wouldn't take one to a cat fight, as the cats would probably win while I was trying to clear jams. But I love them; they are the product of another age.
Jim