20 mm Polsten

Polsten
Polsten
	A Canadian towed anti-aircraft mounting featuring three Polsten cannons.
Type	Autocannon
Place of origin	Poland; United Kingdom
Service history
In service	1944 - 1950s
Production history
Designed	1939-1941?
Manufacturer	John Inglis
Unit cost	£60 - £70
Specifications
Mass	57 kg (126 lb)
Length	2.1 m (6 ft 11 in)
Barrel length	1.45 m (4 ft 9 in) (barrel)
Calibre	20 mm (0.78 in)
Action	API blowback
Rate of fire	450 rpm
Muzzle velocity	830 m/s (2,700 ft/s)
Effective firing range	1,000 m (3,281 ft)
Maximum firing range	2,000 m (6,562 ft)
Feed system	60 round drum magazine or 30 round box magazine

The Polsten was a Polish development of the 20 mm Oerlikon gun. The Polsten was designed to be simpler and much cheaper to build than the Oerlikon, without reducing effectiveness.

Development

When Nazi Germany invaded Poland in 1939, the Polish design team escaped to the U.K. and resumed work together with Czech and British designers. The need for the Polsten was apparently mooted in June 1941. It went into service in March 1944 alongside the Oerlikon. Both the Oerlikon and the Polsten used similar 60 round drum magazines, although the Polsten could also use a simpler box magazine with 30 rounds. It remained in service into the 1950s.

Use

Compared to the Oerlikon's 250 parts, the Polsten had only 119, but it matched the Oerlikon's effectiveness and reliability. The simpler design of the Polsten cannon made its production much cheaper. The cost of one Oerlikon cannon was about £350, while the cost of the Polsten was between £60 and £70. In January 1944, the 21st Army Group decided that only 20 mm Polsten guns would be used as a standard light anti-aircraft gun in place of the Oerlikon to simplify supply. It was used by the anti-aircraft platoons of some British infantry battalions during the Western European campaign of 1944-45. It equipped airborne units in the anti-aircraft role, and was employed in Operation Market Garden. The gun was placed on a wheeled mounting that could be towed behind a jeep.

The Polsten gun was used on armoured vehicles equipped with anti-aircraft guns that were based on the Cromwell/Centaur tank and for the Skink anti-aircraft tank.

The Polsten was also mounted on British LVTs and on early models of the Centurion tank, not coaxially with the main gun but in an independent mount on the left hand side of the turret. Various double, triple and quadruple mounts were developed. John Inglis Limited of Toronto, Ontario, in Canada produced many thousands of guns and some 500 quadruple mountings that saw limited service at the end of the war. These multiple mounts were both trailered and truck-mounted. Polsten Guns, magazines and ammunition boxes were also made in Australia by Holden's Woodville and Beverley plants during World War II. They were used by the Australian Army onshore and on small boats. Several prototype gun mountings were also developed but did not see service.

Etymology

The origin of the name is not entirely clear. Some sources suggest Poland and the "Sten Company" to give Pol-sten, though the Sten gun was not made by a Sten Company. Official (United Kingdom) sources indicate the name to have been a compound based on Poland and the Royal Small Arms Factory Enfield in the same manner as the Bren gun (Brno + Enfield) or Sten (Shephard, Turpin + Enfield); also to reflect the gun design being mostly Polish (and the magazine mostly Czech) and the 8 Polish engineers in the design department. The "Sten" ending may also have linked in with the idea of the gun as a cheaper and quicker to produce weapon just like that gun was.

Operators

Former operators

Notes

References

Postan, M. M.; Hay, D.; Scott, J. D. (1964). Hancock, K. (ed.). Design and Development of Weapons: Studies in Government and Industrial Organisation. History of the Second World War, United Kingdom Civil Series. London: HMSO & Longmans, Green & Co. ISBN 978-0-11630-089-8.

External links

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Autocannons	Becker Type M2 Oerlikon 20 mm Type 99 cannon MK 108 cannon
Grenade launchers	Heckler & Koch GMG Mk 19 grenade launcher
Shotguns	Atchisson assault shotgun
Submachine guns	Sterling SMG TZ-45

British Commonwealth artillery of World War II
Tank guns	QF 2-pounder QF 3-pounder QF 6-pounder QF 75 mm QF 3-inch howitzer QF 17-pounder 77 mm HV QF 95 mm howitzer
Anti-tank guns	QF 2-pounder QF 6-pounder QF 17-pounder
Field guns and howitzers	75 mm Gun M1917 QF 18-pounder 25-pounder Gun-Howitzer 25-pounder Short QF 4.5-inch howitzer
Medium and heavy guns and howitzers	BL 4.5-inch medium field gun BL 60-pounder gun BL 5.5-inch medium gun BL 6-inch howitzer BL 6-inch gun Mk XIX 155 mm Long Tom BL 7.2-inch howitzer BL 8-inch howitzer BL 9.2-inch howitzer 240 mm howitzer M1
Mountain guns	75mm Pack howitzer M1 3.7-inch mountain howitzer
Mortars	SBML 2-inch mortar ML 3-inch mortar ML 4.2-inch mortar
Anti-aircraft weapons	Z Battery 20 mm Oerlikon 20 mm Polsten QF 1½-pounder Mk III QF 2-pounder naval gun Bofors 40 mm QF 3-inch QF 3.7-inch QF 4.5-inch Mk II QF 5.25-inch Mk II
Coast defence	QF 6-pounder 10 cwt QF 12-pounder QF 4.7-inch Mk I–IV BL 6-inch Mk VII & Mk XXIV BL 7.5-inch Mk VI BL 8-inch Mk VIII BL 9.2-inch Mk X BL 14-inch Mk VII BL 15-inch Mk I
Railway artillery	BL 9.2-inch Mk XIII railway gun BL 12-inch Mk V railway howitzer BL 13.5-inch Mk V railway gun BL 18-inch railway howitzer