US Machine Gun Platoon

The M2/M30 4.2-inch mortar was a U.S. rifled 4.2-inch (106.7 mm) mortar used during World War II,  Korea, and  Vietnam. It entered service in 1943. It was nicknamed the "Goon Gun" The first 4.2-inch mortar in U.S. service was introduced in 1928 and was designated the M1 Chemical Mortar. 

The M2 could be disassembled into three parts to allow it to be carried by its crew. The mortar tube weighed 105 pounds, including a screw-in cap at the bottom. The cap contained a built-in fixed firing pin. The standard, a recoiling hydraulic monopod that could be adjusted for elevation, weighed 53 pounds . The baseplate had long handles on either side to make it easier to carry; it weighed 175 pounds.

In 1951 advancements made during the Korean War saw the M2 begin to phase out for the newer M30.  Although the M30, at 305 kilograms (672 lb), was significantly heavier than the 151 kilograms (333 lb) M2. Used in Vietnam as Heavy Mortars in Firebases, or as Mobile firepower while mounted in specifically modified M113 APC's.

Due to Geneva Convention articles regarding chemical weapons only High Explosive, Illumination, and White Phosphorous rounds were employed in Vietnam. An additional Chemical Weapons Treaty was enacted in 1997 in which the US eliminated it's stockpile, and declaring over 450,000 Mustard Gas Chemical shells destroyed.