  the .45 g.a.p. (often called the .45 "gap") pistol cartridge was designed by ernest durham, an engineer with cci/speer, at the request of firearms manufacturer glock to provide a cartridge that would equal the power of the .45 acp, have a stronger case head to reduce the possibility of case neck blowouts, and shorter to fit in a more compact handgun. g.a.p. is an initialism for "glock automatic pistol", and the .45 g.a.p. is the first commercially introduced cartridge identified with glock. ==development== the .45 gap has the same diameter as the .45 acp pistol cartridge but is slightly shorter, and uses a small-pistol primer instead of the large-pistol primer most commonly used in .45 acp ammunition. originally, the maximum bullet weight of the .45 gap was . in order to provide terminal ballistics that matched the standard  .45 acp loads, the .45 gap was designed to operate at a higher standard pressureâroughly equivalent to the higher pressures found in .45 acp "+p" rounds. since the .45 gap has a much smaller cartridge volume than the .45 acp, the desired pressure and resulting velocity needed to be achieved through powder selection alone. later development concluded that the .45 gap could also fire  ammunition as does the .45 acp. ===glock .45 gap pistols=== the full-size glock 37 pistol was introduced by glock to use the .45 gap cartridge and was followed by the compact glock 38 and the subcompact glock 39. the manufacturer lists the width of all three pistols as 1.18" wide, compared with 1.27" for the .45 acp glock 21 and glock 30, indicating that glock could shorten the grip width and front to back grip size. glock's .45 gap sized pistols use the same frame as their 9mm/.40cal/.357s
.45_GAP_firearms Pistol_and_rifle_cartridges