Mortar, 81mm M1

History

The American 81mm Mortar M1, like the upcoming 60mm Mortar M2, was based on a French design by Edgar William Brandt (1880-1960). The M1 is a derivative of the French mle 27/31 system (itself a modification of the WW1 Stokes Trench mortar) and slightly modified to suit American needs.

The M1 became the standard mortar battalion for the U.S. military in World War II, and served in the Korean and Vietnam Wars until it was eventually replaced by the M29a lighter, longer-range 81mm system.

As a weapons engineer, Frenchman Brandt was responsible for several advances in the field of mortars and projectiles, leading to the development of various 60mm, 81mm and 120mm systems, as well as the HEAT Rifle grenade and HEAT warhead advanced anti-tank weapon technology. Brandt's designs were heavily copied during World War II and beyond, making them commonplace around the world in the years that followed.

The U.S. Army had experience using the 3" Mk I Stokes Trench Mortar as early as World War I. This type still circulated in the U.S. Army after the war, despite numerous attempts to find a replacement. As a result, the U.S. Army The Army decided to switch to improved ammunition. In 1931, the U.S.

Army acquired four Brandt 81mm prototypes, and with some minor modifications to adapt them to U.S. usage and production methods, this mortar officially appeared as the "81" mm Morser, M1 "in Army terminology. Licensed production by A.B.

Farquhar Company, Pullman-Standard Car Manufacturing and Watervliet Arsenal.

Like the "lighter" M2 system, the M1 consists of three main components - the launch tube, bipod and base plate. When fully assembled, the M1 weighs 136 pounds. The weight distribution is as follows: the tube accounts for 44.5 pounds, while the stand accounts for 46.5 pounds.

The base plate itself is 45 lbs. The overall length of the system is 3 feet 9.5 inches. The muzzle velocity of the smoothbore tube is rated at 700 feet per second. The operator can load the M1 by placing a prepared projectile into the muzzle, allowing for a sustained rate of fire of 18 rounds per minute. The firing pin at the bottom of the primer tube activates the projectile's primer and primer cartridge (the projectile first falls into the tube "primer end"), and the appropriate action begins a round at a predetermined desired angle.

The operator only needs to protect himself after the projectile falls into the tube. This allows for an excellent sustained rate of fire - the maximum rate of fire is 30 to -35 rounds per minute. The M1 has a minimum range of 200 yards and a maximum range of 3,300 yards.

The altitude is +40 to +85, and the horizontal is 14 degrees. The operator uses a bipod-mounted M4 collimator sight (same as the M2 60mm derivative) for precision calculations and adjustments.

The M1 can use a variety of ammunition types, starting with the M43A1 Light HE (High Explosive) round. The 6.87-pound M43A1 retained a 25-yard debris radius and was equipped with a surface fuze. The 10.6-pound M45 and M45B1 Heavy HEs accomplished more explosive strikes at the expense of range (2,558 yards), thanks to delayed fuzes. The 15-pound M56 is another heavy HE round, with more explosive firepower and a more limited range of 1,300 yards.

The fuze of these special projectiles can be adjusted as required. The shell is stabilized along its trajectory by fixed fins at its rear to compensate for the M1's use of a smoothbore tube (i.e. no rifle for inherent directional ballistics).

In addition to traditional HE rounds, the M1 can reach 2,470 yards with the 10.7lb M57 FS White Smoke Roundout or the 10.74lb M57 WP (White Phosphorus Roundout), which also hits 2,470 yards. White phosphorus rounds are as good at targeting infantry as incendiary rounds.

The M301 is a useful illuminated cartridge with an adjustable fuse and 60-second burn time, as well as a deployable parachute that helps delay the fall of the projectile.

The transport of the heavy M1 was solved by the use of a two-person trolley, referred to as the "M6A1 trolley". This allows a minimal number of crews to move the mortar system and allows weapons to be transported to defensive or offensive positions as needed with relatively little pain.

Another option is to be towed by a mule using a specially designed harness. Despite the inherent weight disadvantage of the M1 kit, the firepower of the mortar makes up for any disadvantage, especially if no artillery support is provided in a given operation.

A well-trained and experienced mortar squad can strike targets from shelters, trenches, ravines or slopes and is therefore lethal to the enemy in both the European and Pacific theaters.

For another mode of transport, the M1 can be turned most efficiently on the back of the M3 half-track. These half-tank/half-truck "dumb" vehicles take on the inglorious task of transporting just about anything under the skies of war.

From the rear of the M3, the M1 can be fired without requiring the crew and gun to leave the vehicle, offering some "hit and run" tactical advantages. In any case, this way of using the M1 proves to be very useful for any company commander.

A shortened version of the M1 was introduced as the T27 "Universal", but in limited quantities, it was never ordered for mass production. A special tube extension system was also developed for the M1 base, but is rarely used in practice.

The 81mm mortar M1 was complemented by the lighter 60mm mortar M2 on the battlefield from 1940. The M2 is a more "portable" piece of equipment, capable of effective indirect fire at close range and capable of operating closer to frontline infantry action, with portability being a major selling point.

Mortar, 81mm M1 size

Roles

Dimensions

Performance

Changes