The .50 GI was born out of the idea that if .40 was better than 9mm, and .45 was better than .40, then .50 must be better then .45. It should not be compared to the .500 S&W, .50 Beowulf or the .50 Action Express as it has much less power. The cartridge is comparable to the .45 ACP +P cartridge, but with a larger diameter bullet.

8" SBR with .50 GI magazine.

Carbine with AR-15 magazines converted to take .50 GI

The .50 GI magazine holds 14 rounds and the AR-15 magazine holds 9 rounds.

The 16" upper will sell for $750 and with one magazine. You can see the contact details of the manufacturer, RMW Xtreme Inc., at the beginning of the below video.

Thanks to Giesler for the link.

Hat Tip: Photos from 475AR @ .50 GI Forum

Click to expand the image

The .50 GI round should not be compared to the Desert Eagle’s .50 Action Express or the .500 S&W. It is slightly more powerful than the .45 ACP.

Wikipedia information on the .50 GI:

.50 GI
Type	Handgun
Place of origin	 United States
Production history
Designer	Vic Tibbets / Alex Zimmermann
Designed	2004
Manufacturer	Guncrafter Industries
Specifications
Case type	Rebated, straight
Bullet diameter	.515 in (13.1 mm)
Neck diameter	.526 in (13.4 mm)
Base diameter	.526 in (13.4 mm)
Rim diameter	.480 in (12.2 mm)
Case length	.899 in (22.8 mm)
Overall length	1.221 in (31.0 mm)
Ballistic performance
Bullet weight/type	Velocity	Energy
275 gr (17.8 g) JHP	900 ft/s (270 m/s)	492 ft·lbf (667 J)
300 gr (19 g) JHP	860 ft/s (260 m/s)	493 ft·lbf (668 J)

The kit will retail for $595.

Hat Tip: Foodpounds