The HELLHOUND 40mm Low Velocity Multi-Purpose Grenade is a fixed type ammunition designed to be fired from a 40mm Grenade Launcher M79, M203 (attached to the M16/M16A1/M16A2 rifle) or Milkor MK-1/[MGL-140]. The round consists of an A5-filled metal projectile body with a rotating band, a point-initiating-base detonating fuze with Safe and Arm technology, and a cartridge case assembly. Upon impact with the target, the firing pin is driven into the detonator, which in turn initiates the spit back charge, producing a jet which initiates the explosive train from the base forward, resulting in an armor-piercing jet of molten metal and fragmentation of the projectile body. With twice the fill amount of an M433 and a 40% increase in the shrapnel pattern and a lethal diameter out to 10 meters, the HELLHOUND will provide superior performance against both Troops in the Open and MOUT type engagements, while providing superior door-breaching capabilities.
from Master Blaster on military.com