The M198 is a medium-sized, towed 155 mm artillery piece, developed for service with the United States Army and Marine Corps. It was commissioned to be a replacement for the World War II-era M114 155 mm howitzer. It was designed and prototyped at the Rock Island Arsenal in 1969 with firing tests beginning in 1970 and went into full production there in 1978. It entered service in 1979 and since then 1,600 units have been produced. The M198 was replaced in US and Australian service by the M777 howitzer. Description The M198 155 mm howitzer weighs less than , allowing it to be dropped by parachute or transported by a CH-53E Super Stallion or CH-47 Chinook. The M198 is a towed howitzer that is transported tail first. The gun tube can be rotated over the howitzer's trail legs to reduce its length, though this requires removal of the muzzle brake, or left in the firing position for faster deployment. When firing, the weapon is lowered onto its baseplate rather than being anchored to the ground, allowing for rapid emplacement. The breech is operated manually via a screw type mechanism that rests low in an ergonomic position. The M198 fires separate-loading (non-fixed) ammunition and can be loaded with a variety of propellants and projectiles. The effective range is 18.1 kilometers when firing standard projectiles, which increases to 30 kilometers when firing rocket-assisted projectiles and guided ammunition. With the 52-caliber modification the range can surpass 40 kilometers. The weapon system requires a crew of 9 and is capable of firing at a maximum rate of four rounds per minute, two sustained. The M198 was deployed in separate corps- and army-level field artillery units, as well as in artillery battalions of light and airborne divisions. It provided field artillery fire support for all Marine Air-Ground Task Force organizations until the adoption of the M777 howitzer. Ammunition types High explosive (HE) (M-107 NC/DC): Explosive Composition B material packed into a thick, internally scored shell which causes a large blast and sends razor-sharp fragments at extreme velocities (5,000–6,000 meters per second). The kill zone has an approximate radius of 50 meters, and the casualty radius is 100 meters. The Marine Corps and US Army also uses the M795 High Explosive round. Rocket-assisted projectile (RAP) A high-explosive rocket-assisted (HERA) M549 round with a greater range than the normal HE. The maximum range is . White phosphorus