M224 60-mm mortar
The M224 60-mm smoothbore mortar is one of the family of mortars developed to replace equivalent World War II-era weapons. The M224 benefits from US experience in the Vietnam War, which indicated the need for a reliable, lightweight weapon at the infantry company level. It can be fired from the standard baseplate and mount or handheld from a smaller baseplate. The mortar can weigh as little as 18 lb (8.2 kg) and be carried by one man.
The weapon can be either drop-fired or trigger-fired. Both the M64 optical expended altogether, including one that pierced the rear of a T-72 tank turret and thousands that devastated “soft-skinned” vehicles and other targets.
But the gun was very unreliable. In questioning 95 pilots and 82 maintainers for its April 1992 report, the GAO found that 56 pilots (59%) and 72 maintainers (88%) had encountered problems with the gun. Several battalion commanders reported breakdowns of over half of the guns during missions; in one case, all 18 guns suffered failures during the same mission.
SPECIFICATIONS •
TOTAL GUN SYSTEM WEIGHT 123 lb
(55.9 kg)
receiver 63 lb (28.6 kg)
barrel 35 lb (15.9 kg)
DIMENSIONS length overall 5 ft 4 in
(1.64 m), width 10 in (254 mm),
height 11 Vain (292mm) MUZZLE VELOCITY 2,641 fps (805 mps) RATE OF FERE 625 (+/~25) rounds/
min, cyclic AMMUNITION WEIGHT
round 12.3 oz (351 g)
projectile 8.3 oz (236 g)
sight and the range indicator used for handheld firing are tritium-filled, giving good night-ranging visibility.
The M720 High-Explosive (HE) cartridge has four propellant increments that can be broken off to achieve the desired range. Other rounds include the
M721 illuminating, M722 smoke, M723
White Phosphorus (WP) as well as two practice rounds. Handheld firing is restricted to a single-increment charge, which yields a 900-m range. The M734 fuze can be set for Proximity Burst
(PRX), Near Surface Burst (NSB),
Impact Burst (IMP), or a half-second Delay After Impact (DLY) for ground penetration.
DEVELOPMENT •
Begun in 1970 by the WatervlietArsenal, Watervliet, New York, with design approval in 1973. Type classification came in 1977, the first unit equipping in 1981. The US Army procured a total of 1,590 M224s, with the Marine Corps purchasing an additional 698.
SPECIFICATIONS •
WEIGHT conventional 46.5 Ib (21.1
kg), handheld 18.0 Ib (8.2 kg) DIMENSIONS bore 60 mm, barrel
length 3 ft 4 in (1.02m) RATE OF FIRE max 30 rounds/mm for
4 min; sustained 20 rounds/min
ELEVATION +45°/ + 85° (800/1,511
mils), traverse 7° (125 mils) to each side
RANGE (M?20 HE ROUND) conventional 3,817 yd (3,490 m); handheld 984 yd (1,340 m); minimum 76 yd (70 m)
SIGHTS M64 with 17° (300-mil) field of view and 1.5-power magnification
M252 81-mm mortar
The M252 Improved 81-mm mortar is an “off-the-shelf” purchase of the British LI 6 mortar. The smoothbore, muzzle-loaded weapon replaced the M29 as the standard battalion-level mortar in the US Army and US Marine Corps.
The M252 combines the British barrel and bipod with a US-designed and -built M3A1 circular baseplate and M64A1 optical sight. The barrel has a distinctive flared blast attenuator; the lower half is finned to dissipate heat and reduce weight. Compared to the M29, the M252 is more stable and accurate and fires improved ammunition to a greater range.
Ammunition for the M252 includes not only all of the M29 projectiles but also the M821 High-Explosive (HE) bomb with the M734 multioption fuze and 49yd (45-m) lethal radius, the M819 smoke
and M853 600,000-candlepower illumination projectiles. To gain a one-shot, non-line-of-sight antitank capability, the US Army tested the Royal Ordnance (in partnership with Alliant Techsystems) Merlin 81-mm terminal homing round beginning in 1991.
50 USMC LAV-25 light armored vehicles carry the M252 mortar mounted in the rear compartment and firing through roof hatches. The vehicle carries 90 mortar rounds. The first was delivered in July 1987.
DEV
ELOPMENT •
US testing began in 1977 and led to type classification in 1984 and initial operational capability in 1987. Manufactured by Royal Ordnance, Great Britain, and Watervliet Arsenal, Water-vliet, New York. The US Army procured nearly 1,100 M252s, while the Marines purchased 800.
COMBAT EXPERIENCE •
LAV-Ms of the 1st Marine Expeditionary Force supported Marine Corps and Gulf State infantry units on their drive toward Kuwait City in February 1991.
SPECIFICATIONS •
CREW 5
WEIGHT 91 Ib (41.3 kg) DIMENSIONS bore 81 mm, barrel
length 4 ft 6 in (1.37m) RATE OF FIRE sustained 15 rounds/
min; max 33 rounds/min
ELEVATION +45 7 + 85° (800/1,511
mils), traverse 7° (125 mils) to either side
RANGE M29 ammunition 6,124 yd (5,600 m); M821 or M889 HE 6,151
yd (5,625 m); M835A1 5,960 yd
(5,450 m); M819 5,577 yd (5,100 m);
practice 437 yd (400 m)
ML20/121 120-mm mortar
The M120 (towed) and M121 (mounted in the Ml064 armored personnel carrier variant) mortars are “off-the-shelf” purchases (Nondevelopment Item/NDI) of Soltam of Israel’s K6 and TT6 mortars. (The Israeli mortars were in turn derived from the Finnish Tampella designs.) The smoothbore, muzzle-loaded weapon replaces the rifled 4.2-in (107-mm) M30 that dates back to World War II.
Like the 81-mm M252 program, NDI selection strove to cut the deployment time for a new heavy mortar. Unfortunately, initial Army dissatisfaction with the three NDI candidates and funding cutbacks delayed procurement for several years.
The M120′s smoothbore steel-alloy tube rests its breech on a circular baseplate and meets a broad-legged bipod about three-quarters up the barrel. Both the towed Ml20 and carrier-mounted M121 use many of the same components, the principal difference being a fully tra-versable base in the mortar carrier.
Ammunition consists of M933 High-Explosive (HE) set offby the M745 point-detonating fuze, M934 HE using the mul-tioptional M734 fuze that is common to all new US mortars, M929 smoke, and M930 illuminating rounds. Probable range error amounts to 1% (80 yards at maximum range) while azimuth deflection is 0.45%. The Swedish Strix terminal homing antiarmor mortar round is being studied for possible use in the M120/ M121.
Ml 20 is the towed version mounted on a thick, 137-lb (62.1-kg) baseplate. It can be towed using the two-wheel, torsion-bar-sprung M286 trailer that also carries six rounds of ammunition. Ml21 is mounted in a modified M106A2 mortar carrier (part ofthe Ml 13 family), which is upgraded to M113A3 standards. The M121 replaces the M30, while 69 120-mm rounds replace 88 107-mm rounds. Conversion plans envision 1,530 M106A1/ A2s being converted to Ml 064 in FY 1993-98.
DEVELOPMENT •
Because most of the world’s heavy mortars use 120-mm ammunition, the US Army elected to replace the 107-mm M30 with a 120-mm
NDI weapon in September 1984. US Arniy testing began in 1986 of NDI submissions from three teams: Spain’s Es-peranza y Cia, SA, and General Defense Corp.; France’s Thomson Brandt and Honeywell Defense Systems; and Soltam International with Martin Marietta. Test results in 1986 showed that none of the three weapons met the Army’s criteria and forced a delay of almost two years.
The Army chose the Soltam-Martin Marietta weapon in April 1988. Water-vlietArsenal, Watervliet, NewYork, builds the mortar under license while Martin Marietta supplies the ammunition. The 199th Infantry Brigade (Motorized), later the 2nd Armored Cavalry Regiment (Light), deployed the towed M120 in September 1991. An original goal of 2,606 mortars dropped to 1,725 with a decline in the force structure.
COMBAT EXPERIENCE •
Israel has used its 120-mm mortars extensively in combat during the Arab-Israeli wars as well as in Lebanon.
SPECIFICATIONS •
CREW 4
WEIGHT total of towed version 709 Ib (322 kg) including 390-lb (177-kg) M286 trailer; mortar 319 Ib (145 kg)
DIMENSIONS bore 120 mm, barrel length 5 ft 9 in (1.76m)
RATE OF FIRE sustained 4-5 rounds/ min; max 19-20 rounds/min
ELEVATION +40°/+85° (711/1,511 mils), traverse 360° (6,400 mils) in Ml 064 vehicle
RANGE max 7,918 yd (7,240 m); minimum 197yd (180m)
