The .45 Glock Automatic Pistol (GAP) cartridge was introduced in 2003 as the first cartridge to have the Glock name. This cartridge was developed by Glock because they wanted a .45 caliber bullet in a case not longer than a 9mm or .40 S&W. Glock wanted a cartridge which would not require a grip larger than what they had in their Model 17 or 22 pistols.
The .45 GAP case is much shorter than a .45 ACP, shorter even than the case of a 9x19mm! Exclusively small primers are used, but essentially all other measurements of the case are the same. .45 GAP and .45 ACP bullets are the same, and bullets weigh between 165 and 230 grains. .45 GAP cartridges generate about 400 to 500 foot pounds of energy at the muzzle, though some loads reach 600 foot pounds of muzzle energy.
Glock's goal in development of the .45 GAP was to provide as much energy as the .45 ACP, or more, while reducing the grip distance from front to back and side to side. In this way, .45 caliber handguns became accessible to more shooters of small stature.
Response to the .45 GAP upon its introduction was generally positive, and .45 GAP pistols were produced by a few firearm manufacturers other than Glock. However, Glock is currently the only manufacturer of .45 GAP handguns. The law enforcement community has given the most favorable reception of the .45 GAP. Five state law enforcement agencies have chosen the Glock 37 chambered in .45 GAP because it has the power of the .45 ACP in a more compact frame. The New York State Police replaced their Glocks chambered in 9mm for Glocks chambered in .45 GAP, and state agencies in Florida, Georgia, South Carolina, and Pennsylvania have set aside their .40 S&W pistols for the .45 GAP Glock 37.