The M1A1 is a recoilless rifle. A recoilless rifle is a light-weight artillery system designed to eject a counter-mass from the rear of the weapon when fired which creates a forward thrust that counteracts most of the recoil. This principle of operation allows the weapon to operate with less structural mass for the gun tube and mount than a conventional artillery piece. This allows greater ease of transport and enhanced utility for mobile combat units such as paratroops and special forces. Some recoilless rifles can be carried by an infantryman while larger weapons can be mounted on vehicles such as jeeps or towed. The most common design of the recoilless rifle vents some portion of the propellant gases to the rear of the tube creating a forward thrust which is nearly equal to the rearward thrust of the recoil. Thus, the recoil is nullified. This eliminates the need for a heavy and complex recoil damping mechanism seen on other conventional artillery pieces. The casing of a recoilless rifle shell is often perforated to allow the venting of propellant gases to create the rearward thrust. Some projectile velocity is lost to counteract recoil, so recoilless rifles generally have less range than conventional artillery.
M1A1:
The M1A1 was first introduced in 1943. It replaced the M1. The M1A1 is one of the most iconic anti-tank weapons of WWII. It fires a rocket propelled shaped charge warhead. This is also known as a HEAT High Explosive Anti-Tank ammunition. A hand grenade with similar explosive power was too heavy to throw or launch from a rifle grenade adapter. The M1 provided a solution to these design factors. The M1A1 was electrically fired from the shoulder in standing, kneeling or prone position. Rockets for the M1A1 weighed 3.5 pounds and were capable of penetrating the heavy armor of German tanks. The M1A1 had a range of about 300 yards. German forces captured M1 Bazookas and quickly developed their own anti-tank weapons, the most well known was the Panzerschreck. The production M1A1 was 54 inches (1.37 m) long and weighed only 12.75 pounds (5.8 kg).
M1A1 Bazooka Rocket:
