A common question that we get here at Glockmeister is "what is the difference between .45 ACP and .45 GAP?"
.45 ACP- The .45 ACP (Automatic Colt Pistol, also known as 45 Auto) cartridge was designed by John Browning in 1904. In 1911 the US Army adopted the M1911 pistol which utilized the .45 ACP cartridge and the rest is history. The .45 ACP is one of the most storied calibers in the world thanks to its stopping power, accuracy, moderate recoil, and low muzzle rise. The GLOCK models 21, 30, 36, and 41 are all chambered in .45 ACP and feature GLOCK's Safe Action Trigger system. Models 21 and 41 carry a standard capacity of 14 (13+1) while the 30 and 30S carry 11 (10+1). The single stack model 36 holds 7 (6+1) rounds.
.45 GAP- The .45 GAP (GLOCK Automatic Pistol) cartridge was designed by Ernest Durham in 2002 at the request of GLOCK. GLOCK requested that this new cartridge equal the .45 ACP in terms of power, have a stronger case head to reduce the possibility of case neck blowouts, and that it fit into a smaller frame than the larger .45 ACP pistols. The resulting pistols manufactured by GLOCK for the .45 GAP cartridge are the Model 37, 38, and 39. These pistols feature the same frame size as the smaller 9mm, 40SW, .357SIG GLOCKs and have a slightly wider slide which is contoured at the bottom to fit the smaller frame. This makes the .45 GAP pistols much smaller than their .45 ACP counterparts and suitable for those with smaller hands. All GAP pistols also come stock with the GLOCK extended slide stop lever. The full-size model 37 holds 11 (10+1), the compact model 38 holds 9 (8+1), and the sub-compact model 39 holds 7 (6+1) rounds.