40 mm

The 40 mm grenade is a military grenade caliber for grenade launchers in service with many armed forces. There are two main types in service: the 40×46mm, which is a low-velocity round used in hand-held grenade launchers; and the high-velocity 40×53mm, used in mounted and crew-served weapons. The cartridges are not interchangeable. Both 40 mm cartridges use the High-Low Propulsion System.

The less powerful 40×46mm is used in hand-held weapons such as the M79, M203, and the multi-shot M32 MGL.

The more powerful 40×53mm is used in automatic grenade launchers mounted on tripods, vehicles or helicopters, such as the Mk 19 grenade launcher. In these roles, the rounds are linked together with a metallic disintegrating link.

A medium velocity 40×51mm 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 40×46mm rounds.

U.S. military rounds designated specifically for the M79 launcher includes:

U.S. military rounds designated specifically for the M203 launcher includes:

The U.S. Army ARDEC began development of a 40 mm airburst fuse in 2011 to improve the ability of grenade launchers like the M203 and M320 to engage targets in defilade. Called Small Arms Grenade Munitions (SAGM), they double the lethality of the standard M433 grenade round by adding a small "smart" fuse sensor that detonates in the air to hit targets in cover or behind obstacles. The airburst function is similar to the XM25 CDTE, which has an onboard laser system to determine the distance to the target, but SAGM is considered complementary to the XM25 rather than competing against it, as the XM25 provides low-angle fire while 40 mm launchers fire a lobbing trajectory. Engineers integrated sensors and logic devices to scan and filter the environment and then autonomously airburst the fuse without needing to be told to by the firer, thereby not requiring the soldier to carry extra weapon accessories. SAGM enables soldiers to accurately incapacitate personnel targets in defilade at ranges between 50 to 500 meters. The round is engineered with three firing modes: airburst; point detonation; and self-destruct. A successful demonstration occurred in November 2013. Although the SAGM sensor does not need a laser rangefinder or any pre-fire programming sequence, it does require some skill by the user to aim and fire the round correctly so that it can detect the wall or obstruction to detonate in the air. The SAGM was to undergo evaluation in July 2015 and, if successful, transition into an official Army program of record by the end of the year. Not only does the fuse burst over walls, but it can detonate when passing cover like trees, bursting just as it senses and passes the trunk. The sort of sensor SAGM uses to differentiate clutter from triggering obstacles is highly classified, but shows airburst reliability of 76 percent.

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Wikipedia