50 GI
The 50 GI is very much like the 45 ACP, albeit with one obvious difference: it is .50 cal instead of .45. The 50 GI failed to gain widespread popularity following its introduction to the market in 2004, although Guncrafter Industries and Magnum Research both offer handguns chambered for it. The former also offers a Glock 20/21 conversion kit. Expect a 1,200 fps muzzle velocity from the 185 grain bullet, or 900 fps from the 275 grain.