The .50 GI pistol cartridge was developed by Vic Tibbets and Alex Zimmermann of Guncrafter Industries. The .50GI was introduced at the 2004 SHOT Show alongside the Guncrafter Industries Model No. 1, a variation of the M1911. The round has a rebated rim that is the same diameter as that of the .45 ACP. This allows the larger cartridge to be chambered in an existing .45 ACP firearm by simply switching the barrel, rather than a full upper replacement.
In 2006, Guncrafter Industries introduced its 1911 Model No. 2 which sports a full length light rail/dust cover and is chambered for the .50 GI cartridge. Both the M1 and the M2 can be fitted with Guncrafter Industries' .45 ACP conversion unit, the .45 ACP magazines hold 8 rounds.
Physically, the .50 GI round is slightly shorter than the .45 ACP but is wider. The M1 and M2 magazines can hold 7 rounds. The Glock conversion can hold 8 rounds in the standard magazine and 9 with the extended base pad.
The .50GI operates at pressures comparable to the .45ACP, around 15,000 psi (100 MPa). Felt recoil is not unlike that of the .45ACP. The .50GI has developed a reputation for accuracy, though this may be due to the high precision of the semi-custom and very expensive Guncrafter pistols themselves. In one test, the 300 grain (19 g) JFP (jacketed flatpoint) gave a 25-yard group of 2.24 inches, and the 300-grain JHP (jacketed hollowpoint) and 275-grain JHP gave a 25-yard group of 2.14 inches.
The penetration in gelatin (but not necessarily the kinetic energy) of the .50GI is significantly different than the .45ACP. While it is one of the few examples of the largest caliber projectile (.50) in a semiauto handgun (or any firearm not considered a Destructive Device by the BATF, for that matter) it was purpose built to have a recoil impulse and kinetic energy substantially less than the magnum .50 caliber rounds such as the 50 Action Express (semiautomatic) or .500 S&W Magnum (revolver). Factory loaded ammunition has a kinetic energy of around 500 ft·lb. The Guncrafter Industries' website has suggested loads that push the cartridge into the realm of the .44 Magnum.
In one evaluation the following performance difference was noted between the .45ACP and the .50GI: "It actually pounded my steel target with so much force that it knocked the entire 100-pound plate and stand combo hard enough to make it furrow the ground it stood upon. Folks, these .50 calibers really do hit that hard. [The 300 grain TMJ] caused dings in steel targets that normally fracture .40 and .45 cal rounds into so much dust."
The cartridge is rarely used in law enforcement or for personal defense due to limited availability of ammunition and guns chambered for the cartridge. Currently, the only commercial handguns available in this caliber are Guncrafter Industries' own Colt 1911 handgun variants and its Glock 21 / Glock 20 conversion upper. However, at least one gunsmith has produced a custom revolver for the .50GI.
- 185 gr (12 g) JHP, 1200 ft/s, 591 ft-lb
- 275 gr (18 g) JHP, 900 ft/s, 495 ft-lb
- 300 gr (19 g) JFP, 700 ft/s, 350 ft-lb
- 300 gr (19 g) JHP, 860 ft/s, 493 ft-lb