M4 BEOWOLF

Type	Rifle
Place of origin	United States

Designed	2001
Produced	2001

Parent case	.50 Action Express
Case type	Rebated rim, straight
Bullet diameter	.500 in (12.7 mm)
Neck diameter	.525 in (13.3 mm)
Base diameter	.535 in (13.6 mm)
Rim diameter	.445 in (11.3 mm)
Case length	1.65 in (42 mm)
Overall length	2.125 in (54.0 mm)
Primer type	Large pistol magnum

The .50 Beowulf [12.7 x 42 mm Rb] is a rifle cartridge developed by Alexander Arms for use in a modified AR-15 rifle. The cartridge utilizes a rebated rim, sized to match the rim of the 7.62x39mm and 6.5 mm Grendel rounds. It is very similar in dimensions to the .500 S&W Magnum revolver cartridge.
According to the manufacturer, it was descended from the .50 Action Express, a cartridge originally developed for the Magnum Research Desert Eagle pistol, with significant modification to improve functionality and safety in the AR-15 platform.
The round is intended to improve stopping power greatly at short-to-medium range as compared to the standard 5.56mm. One of its advertised uses is at vehicle checkpoints, since the heavy bullet's flight path is not easily deflected by auto glass or standard vehicle body panels.