M198 - 155 mm Howitzer

Development

Development of a 155 mm howitzer to replace the 155 mm howitzer M114/M114A1 began in 1968 under the direction of the Project Manager for Cannon Artillery Weapon Systems of the United States Army Armament Command at Rock Island, Illinois. A test rig was built to demonstrate how a lightweight towed 155 mm howitzer could fire the increased range of ammunition, with reasonable probability of stable dynamics and structural soundness. Design and fabrication of an advanced development prototype began in 1969 and firing trials commenced in 1970. Rock Island was responsible for the carriage and recoil mechanism, Frankford Arsenal for the fire-control equipment, Watervliet Arsenal for the ordnance and Picatinny Arsenal and the Harry Diamond Laboratory for the ammunition. The first two prototypes were delivered in April and May 1972 and were followed by a further eight prototypes. After trials, the XM198 was standardised as the M198, and production commenced at Rock Island Arsenal in 1978 with first production weapons completed in July 1978. Since then large numbers have been built for the home and export markets but there has been no US Army funding since FY82.

The M198 replaced M114A1s in separate field artillery batteries assigned to corps/army and the general support field artillery battalions of the light divisions. It is deployed in 24 gun battalions, with every battalion having three batteries each with eight guns. The first battalion of M198s became operational at Fort Bragg in April 1979. The first Marine Corps battalion to be equipped with the M198 was the 2nd Battalion, 10th Marines, at Camp Lejeune. Production of the M198 was carried out at Rock Island Arsenal which also manufactured all components with the exception of the ordnance (which comes from Watervliet Arsenal), fire-control system and tyres. In February 1992, the 1,672nd M198 rolled off the production line at Rock Island Arsenal. During FY91, a total of 120 was manufactured followed by 120 M198s in FY92. In early 1993, the US Army had 745 systems in service, with the Marine Corps having an additional 566 weapons. Both these figures include reserve systems. In June 1992, Watervliet Arsenal was awarded a $5.402 million increment as part of a $5.509 million firm fixed price contract for 292 product improvement kits for the M198 towed howitzer with all work completed by April 1995. In December 1993, Watervliet Arsenal was awarded a $5.525 million increment as part of a $10.730 million firm fixed price contract for 602 product improvement kits for the M198 towed howitzer (quantity increased from the original 292) with the work completed by April 1995. Production of the M198 has now been completed although it could commence again if further orders were placed. In US Army service the 155 mm M198 will be supplemented by the Vickers Shipbuilding and Engineering Limited 155 mm Ultralightweight Field Howitzer which was selected in March 1997 following extensive trials with competing weapons.

Description

The weapon is mounted on a split trail carriage, fitted with a two-position rigid suspension system which can be rotated upwards to raise the wheels. This allows the weapon to rest on a non-anchored firing platform. When travelling the ordnance remains forward, but for storage it can be traversed through 180 and locked in position over the trails. The carriage consists of the top carriage, elevating mechanism, equilibrators, traversing mechanism, bottom carriage, wheel suspension assembly, speed shift, trails and firing base. An auxiliary power unit, the MC-4000, has been developed for use on the M198 during amphibious operations, but no procurement decision has yet been made. The recoil mechanism is of the hydropneumatic type with a variable recoil length. The autofrettaged ordnance has a screw-on double-baffle muzzle brake, and a screw breech mechanism with a conventional obturator pad and split ring seal obturator. The fire-control equipment includes an M137 panoramic telescope with a magnification of x4 and a 10 field of view, two elevation quadrants (M17 and M18) and an M138 elbow telescope with a magnification of x8 and a 6 field of view. The internal configuration of the Cannon Assembly M199 is in accordance with the German/British/American/Italian quadrilateral agreement and will fire all current standard and developmental ammunition of the anti-material and anti-personnel types. The weapon can fire the following types of ammunition:

Anti-tank (M718) (containing nine anti-tank mines) with the projectile weighing 46.72 kg and a muzzle velocity of 660 m/s and a maximum range of 17,740 m

Anti-tank (M741) (containing nine anti-tank mines) with the projectile weighing 46.72 kg, muzzle velocity of 660 m/s and a maximum range of 17,740 m

Copperhead Cannon Launch Guided Projectile (M712) to a range of 16,400 m

HE (M107) with the projectile weighing 42.91 kg, muzzle velocity of 684.3 m/s and maximum range of 18,100 m

HE (M449) (containing 60 anti-personnel grenades) with the projectile weighing 43.09 kg and a maximum range of 18,100 m

HE (M483) (containing 88 dual-purpose grenades) with the projectile weighing 46.53 kg, muzzle velocity of 660 m/s and maximum range of 17,500 m

HE (M692) (containing 36 anti-personnel mines) with the projectile weighing 46.5 kg, muzzle velocity of 660 m/s and a maximum range of 17,740 m

HE (M731) (containing 36 anti-personnel mines) with the projectile weighing 46.5 kg, muzzle velocity of 660 m/s and a maximum range of 17,740 m

HE (M795), registration projectile for M483 and maximum range of 22,400 m

HERA (M549 series) (RAP) with the projectile weighing 43.54 kg, maximum muzzle velocity of 826 m/s and maximum range of 30,000 m

DPICM (Dual-Purpose Improved Conventional Munition) M864 (type-classified late in 1987)

Illuminating (M118 series) with the projectile weighing 46.26 kg, muzzle velocity of 684.3 m/s and maximum range of 18,100 m

Illuminating (M485 series) with the projectile weighing 41.73 kg, muzzle velocity of 684 m/s and maximum range of 17,500 m

REMBASS (XM694E1), under development

Smoke WP (M110 series) with the projectile weighing 44.4 kg, muzzle velocity of 684.3 m/s and maximum range of 18,100 m

Smoke BE (M116 series) with the projectile weighing 42.22 kg, muzzle velocity of 684.3 m/s and maximum range of 18,100 m

Smoke (M825), base ejection, with a muzzle velocity of 797 m/s and a maximum range of 22,600 m

Improved M198

Late in 1994, it was stated that the US Army and Marine Corps were considering a number of improvements to the 155 mm M198 towed howitzer. These include an electronic fire-control system, automatic digital interface, faster primer loader or laser ignition, projectile load assist mechanism and power suspension. By mid-1997, none of these proposed improvements had been carried out to the M198. In 1995 however, it was decided that the US Marine Corps fleet of 601 M198s would receive 27 separate modifications to increase safety, enhance transport, reduce cyclical repairs and extend the serviceable life of the howitzers. All these modifications were carried out by January 1997 under the M198 Product Improvement Program (PIP).

Extended Range Modification Program

TEXT : Rock Island Arsenal has proposed a new extended-range cannon programme to increase the range of the M198 without sacrificing weight. Listed below are some of the key features of the upgrade programme:

(1) Increased range using a new 155 mm/52 calibre ordnance. This will enable a range of 30,000 m to be achieved using unassisted ammunition, 37,500 m using the M549 RAP and 40 to 50 km using a future RAP/BB projectile
(2) Maintains current system weight
(3) Minimised retrofit cost
(4) Achieved compatibility with future advanced armament
(5) Maintains existing logistic support and training needs
(6) Extends useful life of the M198 howitzer

M198 with computer

In mid-1997, four M198s fitted with a computer system and a hydraulic emplacement pump that allow quicker firing and wider dispersion were undergoing trials with the US Marines. The computer system consists of a Global Positioning System (GPS) and an Aiming Pointing System (APS). As the M198 is fitted with a GPS it always knows its location. The APS contains a ring laser gyrocompass used for direction finding and this also allows the howitzer to know which way it is pointing.

The M198 section chief now uses a hand-held navigator called a plugger to position the gun and communicate with the fire direction centre. The hydraulic emplacement pump helps the howitzer team to move faster from one firing position to the next so making the weapon more survivable.

SPECIFICATIONS :

Calibre: 155 mm
Barrel length: 6.096 m
Muzzle brake: double-baffle
Recoil: hydropneumatic
Breech mechanism: screw
Carriage: split trail
Shield: no
Weight:
(travelling order) 7,163 kg
(firing position) 7,163 kg
Length:
(travelling) 12.34 m
(firing) 11 m
(with ordnance over trails) 7.44 m
Width:
(travelling) 2.794 m
(firing) 8.534 m
Height:
(travelling) 2.9 m
(min firing) 1.803 m
(with ordnance over trails) 2.121 m
Ground clearance:
(travelling) 0.33 m
Track: 2.362 m
Tyres: 16.5 x 19.5
Elevation/depression: +72/-5
Traverse:
(total) 45
Rate of fire: 4 rds/min
Max range:
(M107 projectile) 18,150 m (Z8 charge)
(M483A1 projectile) 22,000 m (Z8C charge)
(M549A1 RAP) 30,000 m (Z8S charge)
Towing speed:
(cross-country) 8 km/h
(improved roads) 72 km/h
(secondary roads) 40 to 48 km/h
Crew: 11
Towing vehicle: M939 5 ton (6 x 6) truck

Status : Pakistan 95 plus 24 delivered in 1997

COMPANY NAME : Rock Island Arsenal