The development of the M198 155mm towed howitzer began in 1968 when a lightweight replacement was sought for the WWII era M114 155mm howitzer. A testbed prototype was developed and constructed at the Army's Rock Island arsenal in 1969 and firing tests began in 1970. Following initial firing tests, two prototype M198 howitzers were delivered to the Army in 1972, and following additional testing, the M198 howitzer entered full time production in 1978. The first Army M198 unit became operational in April of 1979.
Since entering production, over 1,600 units have been manufactured, with the final units coming out of Rock Island in 1992.
The M198 is currently in active service with both the US Army and the Marine Corps though it is being replaced by the M777 ultralightweight 155mm howitzer in selected units.
The M198 155mm howitzer is a towed field artillery piece of a split trail carriage design. The M198 is equipped with a double baffle muzzle brake and a variable length hydropneumatic recoil mechanism. The M198 is transported trail first, with the gun suspended over a single pair of traveling wheels. While deployed forward for firing and transportation, for storage, the gun can be rotated 180 degrees (over the trail.) When fired, the howitzer is not anchored, but rather, rests on the traveling wheels. The M198 cannot be fired while "limbered" (in traveling configuration), but rather, must be emplaced. The M198 does not have a splinter shield, and there is no option to attach one. The breech is a manually operated screw type mechanism. The M198 fires non-fixed (separate projectile and propellant) ammunition and can be loaded with a variable number of propellant bags. The M198 is capable of providing fire support in both indirect and direct fire capacities.
The M198 is air-transportable by C-5 and C-17 aircraft, and can be slung externally by CH-47D and CH-53E heavy lift helicopters (it is not CV-22 Osprey capable.)
The M198 howitzer weighs 15,760 pounds (in both traveling and firing configuration), and is 35.75 feet long in firing configuration (40 feet in traveling configuration and 24 feet in stowed configuration.) The cannon itself has 45 degrees of lateral traverse and can be elevated between 72 and -5 degrees. The normal ground transport for the M198 is the M939 6x6 5-ton truck and the cannon itself requires a crew of 11.
The M198 has a sustained rate of tire of 4 rounds per minute. The howitzer's maximum range is 18,100m when firing standard 95-pound M107 HE and M864 DPICM projectiles, and 30,000m when firing 97-pound M549 RAP rounds.