40mm Caseless Grenade
The 40mm grenade is a military grenade caliber for grenade launchers in service with many armed forces. There are two main types in service: the 40x46mm, which is a low-velocity round used in hand-held grenade launchers; and the high-velocity 40x53mm, used in mounted and crew-served weapons. The cartridges are not interchangeable. Both 40mm cartridges use what the US Army during the Vietnam War called the High-Low Propulsion System.
The less powerful 40x46mm is used in hand-held weapons such as the M79, M203, the M320 grenade launcher, and the multi-shot M32 MGL.
The more powerful 40x53mm is used in grenade launchers mounted on vehicles or tripods, often with automatic firing capabilities such as the Mk 19 grenade launcher, the Mk 47 "Striker" 40 mm Grenade Machine Guns (GMGs), the Heckler & Koch GMG or the South African Vektor Y3 AGL. In these roles, the rounds are linked together with a metallic disintegrating link and fired automatically. The 40x53mm is also used in some mounted helicopter grenade launcher systems, which are electrically powered and primed.
A new 40x51mm cartridge recently (2007) developed in South Africa provides a more powerful alternative for hand-held weapons without increased recoil. A new version of the Milkor MGL chambered for the new round remains backward compatible with existing 40x46mm rounds.
Caseless
Essentially, the grenades for the 40mm x 46mm and 40mm x 53mm grenades are the same, with the cartridge and powder levels being different. The 40mm x 51mm grenade is vastly different, being much lighter weight, but over-all the same.
The rounds are caseless, based off of the 3GL caseless firing mechanism, and designed for use both inside 3GL's, modified 3GL's, and various other 40mm grenades.
