Ordnance ML 4.2 inch Mortar

Ordnance SB 4.2 inch Mortar
300px Ordnance ML 4.2 inch Mortar on mobile baseplate
Type	Mortar
Place of origin	United Kingdom
Service history
In service	1942-
Used by	United Kingdom Australia
Wars	Second World War Korean War Indonesia–Malaysia confrontation
Production history
Number built	about 3,800
Specifications
Weight	Barrel: Mk 2 92 lbs Tripod & mounting: 112 lbs Base plate: No 2 baseplate 120 lbs, with auxiliary baseplate fitted 318 lbs, mobile baseplate 602 lbs
Barrel length	Mk 1 64 inches, Mk 2 68 inches
Calibre	4.2 inch (106.7 mm)
Elevation	45° - 80°
Traverse	10°
Rate of fire	20 rounds for 1 minute, 15 for 3 minutes, 10 for sustained fire
Maximum firing range	4,100 yards (3,750 m)

The Ordnance ML 4.2 inch Mortar was a heavy mortar used by the British Army during World War II, and by other armies postwar.

History

The 4.2 inch mortar was a Smooth Bore (SB) weapon of the Stokes pattern and was designed by the Armaments Research and Development Establishment and produced by the Royal Ordnance Factories.

It entered British service in 1942, where it was used to equip Royal Engineer chemical warfare companies. The Mark 3 became the standard model. The first combat use was at El Alamein, which expended all the HE ammunition in the theatre.

Around mid 1943, the RE chemical warfare companies were disbanded and one heavy mortar company of each Infantry Division's machine gun battalion was equipped with the mortar. This company was organized with sixteen 4.2-in mortars, divided into four Platoons of four mortars each.

In early 1944, Divisions in Italy also held a pool of mortars for issue to other units as required, usually troops in the divisional anti-tank regiment - some regiments even converted one or more batteries to mortars.

The mortars were somewhat slower in reaching the far east, although the Australian forces in the South West Pacific had them before troops fighting in Burma did.

Postwar

After World War II, the mortars were handed over to the Royal Artillery - 170 Mortar Battery used them at the Battle of Imjin River in Korea. They were used during the 1950s, including by airborne artillery, deployed to Kuwait in 1961 and manned by soldiers from air defence batteries during the Confrontation in Borneo in 1965.

Description

The 4.2" Mortar entered production at the end of 1941. Initially it was fielded with a standard baseplate and tripod. The normal detachment was 6 men, and it was transported with ammunition in a 10cwt trailer, usually towed behind a Loyd Carrier. There was also an auxiliary baseplate that fitted around it to increase its area for use on softer ground.

Later an integrated trailer / baseplate was developed, called the Mk 1 Mobile Baseplate. The wheels, which were on suspension arms, were unlocked and raised for firing, Mk1/1 had detachable wheels. The barrel with tripod attached was stowed on top for towing. The mobile baseplate trailer mounting could be brought into action by 2 men.

Ammunition

Both HE (9.1 kg) and smoke (10.2 kg) ammunition was used. Smoke include WP and Base Ejection, and in World War II other types for practice.

Two charges were available. In World War II, both streamlined and cylindrical bombs were available.

Users

World War II

• Australia
• UK

Postwar

• Australia
• Canada
• Ethiopia
• Laos
• Malaysia
• Nepal
• Turkey
• UK

See also

Weapons of comparable role, performance and era

• M2 4.2 inch mortar - US equivalent
• 107mm M1938 mortar - Soviet equivalent

References

• Maintenance Manual for ML 2-inch, ML 3-inch and SB 4.2-inch Mortars