The 45 GAP or 45 Glock Automatic Pistol cartridge is a shortened 45 ACP case that functions in handguns that accept 40 S&W and 9mm Luger magazines. This is a fine idea in view of the difficulty that many shooters, including myself, have in getting a firm grip on the larger handguns that utilize double-column 45 ACP magazines. Maintaining a firm, repeatable, grip on a firearm helps to increase your accuracy with a firearm and this will make you a better shot.

I wish that I invented the phrase: “There isn’t any such thing as a free lunch.” But alas and alack, that was Robert Heinlein. You pick up many benefits when you switch to 45 G.A.P but you lose some things as well. To begin, the chamber pressure of the 45 ACP is in the neighborhood of 21,000 PSI while the chamber pressure of the 45 G.A.P is 23,000 PSI. The difference is not enough to write home about so it is fair to assume that the ‘snappiness’ of the round is similar to the 45 ACP which is often described as ‘more of a push than a shove’. This helps reduce the perception of recoil and helps you reacquire the target quickly for a second shot. As we have talked about in other pages on this website, firearm propellant does not directly follow the Ideal Gas law but it follows it notionally. To restate it for convenience (see Equation 1):