Ordnance ML 4.2 inch Mortar

Ordnance SB 4.2 inch Mortar
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
Wars	Second World War
Production history
Number built	about 3,800[1]
Specifications
Weight	* Barrel weight: Mk 2 92 lbs Tripod & mounting weight: 112 lbs Base plate weight: 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)[2][3]
Elevation	45° - 80°
Traverse	10°
Rate of fire	20 rounds for 1 minute, 15 for 3 minutes, 10 for sustained fire
Maximum range	4,100 yards (3,750 m)

The Ordnance ML 4.2 inch Mortar was a heavy mortar used by the British and other armies.

History

The SB 4.2 inch mortar British entered service in 1942 to equip chemical warfare companies of the Royal Engineers. The Mark 3 became the standard model. The mortar was a Smooth Bore (SB) design of the Stokes pattern. It was designed by the Armaments Research and Development Establishment and produced in Ordnance Factories.^[4]

It was first used at El Alamein and all the HE ammunition in the theatre was expended. Soon after the chemical warfare companies were disbanded and one company of each divisional machine gun battalion was re-equipped with the mortar. Divisions also held a pool for issue to other units as required, usually troops in the divisional anti-tank regiment. However, these mortars did not reach Burma although they were used by Australian forces in the South West Pacific.

After World War II the mortars equipped light batteries of the Royal Artillery. 170 Light 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 Confrontation in Borneo in 1965.

Description

The mortar had an integrated trailer and baseplate called the Mk 1 Mobile Baseplate. The wheels 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. A standard baseplate was available and there was an auxiliary baseplate that fitted around it to increase its area for use in softer ground. The normal detachment was 6 men, but the trailer mounting could be brought into action by 2 men.^[5] In World War II it had its own ammunition trailer.

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

After World War II users included: UK, Australia, Ethiopia, Laos, Malaysia, Nepal, Turkey.

Notes

1. ^ British Mortars of the Second World War
2. ^ Brassey’s p. 92
3. ^ Maintenance Manual for ML 2-inch, ML 3-inch and SB 4.2-inch Mortar
4. ^ Pugh p. 76
5. ^ Pugh p. 76

References

• Pugh, Stevenson (1962). Fighting Vehicles and Weapons of the Modern British Army (First ed.). London: Macdonald. 
• Bidwell, Shelford (1977). Artillery of the World (First ed.). London: Brassey’s. ISBN 0904609049. 
• Maintenance Manual for ML 2-inch, ML 3-inch and SB 4.2-inch Mortars
• Bishop, Chris. The Encyclopedia of Weapons of WWII. http://books.google.co.uk/books?id=MuGsf0psjvcC&lpg=PA194&ots=K4XAweMGaH&dq=Britrish%204.2%20inch%20mortar&pg=PA194#v=onepage&q=&f=false. 
• "British Mortars of the Second World War". WWIIEquipment. http://www.wwiiequipment.com/index.php?option=com_content&view=article&id=91:british-mortars-of-the-second-world-war&catid=47:british&Itemid=59.