The M18 is a World War 2 era recoilless rifle of US origin. It was developed in 1943 as freelance research by two engineers and the weapon proved more useful than other weapon in development at the time. The M18 is the smallest caliber and lightest recoilless rifle ever in widespread use. Compared to the M9 Bazooka it had a much longer effective range, but its spin stabilized round were not as effective against armor.

The M18 is a man portable recoilless rifle of a conventional breech loaded design. The crew of two consists of a gunner and a loader. The M18 has a rifled barrel and a large expansion chamber. The pistol grip and trigger are on the right side of the barrel with the optics mounted on the left. The M18 may be fired from the shoulder, but it is usually fired from its rear bipod and front monopod. A M1917 tripod may be used as well.

The M18 fires 57mm rounds that are pre-engraved and have a perforated case in order to let the gasses expand for reduced recoil. The four types of ammunition include HEAT, HE, WP and target practice. The HEAT rounds can be used up to 450 meters and will pierce 63mm RHA. The HE and WP rounds are effective out to 1 km, but can be fired as far as 4 km.

Although the M18 is much heavier as rocket launchers such as the M9 Bazooka it remains man portable over long distances. The bipod doubles as a shoulder cradle and is padded for some degree of comfort.

The M18 was used in reasonable numbers by US forces during the later stages of World War 2. It was also widely employed during the Korean War. Due to its limited effectiveness as an anti-tank weapon it was replaced by the M20 Super Bazooka and larger M67 recoilless rifle. The M18 has been exported to many US allies and was in production in China. Nowadays the M18 is an obsolete weapon and is usually only found in reserve use or storage.