The .50 GI (12.7×23mmRB) pistol cartridge was developed by Alex Zimmermann of Guncrafter Industries.

The Glock conversion can hold eight rounds in the standard magazine and nine with the extended base pad.

The .50 GI 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.

[4][5] While it is one of the few examples of the largest legally allowed calibers in a semiauto handgun, 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).

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 receiver, and Magnum Research chambers their BFR revolver in this caliber on a custom basis.