Let’s go back to the year 2003. The .40 S&W cartridge introduced in 1990 skyrocketed to first place in popularity among American police service pistols. The almost decade-old .357 SIG cartridge also seemed to be ascendant. It was clear that law enforcement wanted something more powerful than 9mm. This was a trend led by the FBI itself following a 1986 incident in Miami where a lethal 9mm hit failed to stop a determined gunman from murdering two Special Agents and severely wounding many more. Many departments still favored the .45 ACP but bemoaned the large grip frames required to carry greater than eight-round magazines. The big Glock 21, the most popular police .45 at the time, was simply too big for small-handed shooters to do their best work with it.
Glock approached ATK to create a cartridge with .45 ACP ballistics, but short enough overall to fit a “9mm platform” handgun. A team led by Ernest Durham produced the result, the .45 GAP (Glock Auto Pistol). Durham and company had worked some magic with powder and primers to get that power level into the shorter casing, but a 200-grain Speer Gold Dot bonded hollow point at 1000 foot-seconds or better duplicated the devastating stopping power proven on the street by Speer’s older 200-grain .45 ACP. The Gold Dot bullet performed much better than its predecessor and fed better. The price, however, was a “+P” pressure level.
This allowed Glock to use the same size frame as their 9mm service pistol, the G17, but with the wider, heavier slide of the G21 in .45 ACP. Cartridge capacity was ten rounds in the magazine of the full size (4.6” barrel) G37, eight in the compact (Glock 19 footprint) G38, and six in the “baby Glock” size G39.
