Specifications

Caliber:	.50 inches (12.7mm)
Weight:	462 pounds
Length:	11 feet 2 inches
Height:	3 feet 8 inches
Shell:	106×607mmR (HEAT, HEP, HEAP, Canister)
Caliber:	105 mm
Recoil:	Recoilless
Muzzle Velocity:	1,650 feet/second
Carriage:	Tripod
Manufactured by:	Watervliet Arsenal
Status:	Static display
Owner:	Estrella Warbirds Museum

History

The M40 recoilless rifle is a portable, crew-served 105 mm recoilless rifle made in the United States. Intended primarily as an anti-tank weapon, it could also be employed in an antipersonnel role with the use of an antipersonnel-tracer flechette round. The bore was commonly described as being 106 mm caliber but is in fact 105 mm; the 106 mm designation was intended to prevent confusion with incompatible 105 mm ammunition from the failed M27. The air-cooled, breech-loaded, single-shot rifle fired fixed ammunition and was used primarily from a wheeled ground mount. It was designed for direct firing only, and sighting equipment for this purpose was furnished with each weapon, including an affixed spotting rifle.

This particular M40 Recoiless Rifle is shown mounted on a M274 Truck, Platform, Utility, 1⁄2 Ton, 4X4 or "Carrier, Light Weapons, Infantry, 1⁄2 ton, 4x4", also known as the "Mule", "Military Mule", or "Mechanical Mule". The Mule is a 4-wheel drive, gasoline-powered truck/tractor type vehicle that can carry up to 1⁄2 short ton off-road. It was introduced in 1956 and used until the 1980s. This configuration was frequently seen during the Vietnam Conflict. Read more about the M274 Mule at the link above.

Replacing the M27 recoilless rifle, the M40 primarily saw action during the Vietnam War and was widely used during various conflicts thereafter in Africa or in the Middle East. It was replaced by the BGM-71 TOW anti-tank missile system in the US Armed Forces.

The M40 is shaped like a long tube with an M8C .50 cal spotting rifle above. The spotting rifle fires a round whose trajectory closely matches that of the 105 mm round and gives off a puff of smoke on impact with the target. On the left side, there is an elevating wheel, in the center of which is the trigger wheel used to fine adjust the elevation and at the same time firing the spotting rifle when pulled, and the gun when pushed. The mounting is a tripod, but the front leg has a castering wheel. On top of the mount is a traverse wheel. On the center of the traverse wheel is a locking wheel, when the wheel is down, the rifle is locked in traverse, and can only be moved right and left with the traverse wheel. When the wheel is raised, the rifle can be traversed by hand. Austria produced a two-wheeled mount for the M40.