Oerlikon 20 mm

The 20 mm Oerlikon is the most widely used close-range gun in both the US Navy and Royal Navy, which had up to that point only developed inferior guns in comparison. In comparison with the Hispano Suiza, the Oerlikon had a lower rate of fire and muzzle velocity, but was despite these shortcomings an excellent weapons. The American and British built thousands of these during the war, and naturally the surviving Dutch warships also received this gun ( of both US and British origin ) as replacement for the useless light machineguns. There was very little difference between the types of the US Navy and Royal Navy, and below are the specifications listed for the British Mark II. The US versions were designated Mark 2, 3, 4 etc. The specs for one of the British types, the Mk II are listed below, but the guns of various marks and nationalities differed little.

single 20 mm on a minesweeper

Gun specs
Gun type	20 mm Oerlikon Mark II ( British )
Origin	Swiss
Purpose	Close range AA-defence
Bore	20 mm
Bore length	65 calibres ( US version was 70 calibres )
Classes	Most surviving units after 1942
Date in service	During WW II ( with RNN )
Gunweight	68 kg
Initial velocity	2725 feet/sec
Rate of fire	450 rounds/minute
Shell specs
Shell types	20 mm explosive shells
Shell weight	123 grams
Range ( max )	about 3000 metres @ max. elevation
Ammo feed	60 round drums
Mount specs
Designation	Mark 6
Mount type	single mounts ( double were to my knowledge never used )
Mount armor	Armoured shield sometimes fitted.
Elevation	-15 / + 90 degrees
Train	360 degrees continuous
Train method	Manual
Mount weight	767 kg

Diagram
A	Barrel
B	Recoiling barrel spring casing
C	Double-loading interlock
D	Magazine
E	Foresight, with 300, 200 and 100 knot rings
F	Shoulder rests
G	Handgrips
H	Aimer's body strap
I	Trigger
J	Cotter, connecting recoiling side plates to gun bolt
K	Trunnion
L	Fixed pedestal
M	Training cradle

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