The .45 GAP (Glock Auto Pistol) round was designed by CCI / Speer, at the request of Glock, to provide a cartridge that would rival the firepower of the .45 ACP, but would be shorter to fit in a more compact semi-auto pistol. The .45 GAP round is the newest pistol round to be backed by a major firearms producer, Glock. Due to it's new-ness the only pistols to fire it are the Glock 37, 38 and 39. For the practical shooter, the .45 GAP might not be the best choice, due to ammo availability and the somewhat specialized nature of the round. Most .45 enthusiasts choose the .45 ACP. The .45 GAP is sort of like the DeLorean of the pistol ammo world. New, cool, and slightly exotic, but not mainstream and somewhat hard to come by. Muzzle velocity for the .45 GAP is 880 ft / sec to 1,000 ft / sec, and impact energy is 395 ft lbs to 411 ft lbs.