Oerlikon 20 mm/70 (0.79") Mark 1
United States of America
20 mm/70 (0.79") Marks 2, 3 & 4
20 mm/70 (0.79") Mark II

Updated 28 December 2013


USA Twin 20 mm/70 AA with Mark 14 Gyro gunsight
The mounting is probably a Mark 24
Click on this picture for a larger image


British version of the Oerlikon 20 mm/70 on Mark IIA Pedestal Mount
Note the eyepiece/ring sighting system; this weapon depended entirely upon the gunner's shooting ability
Sketch from B.R. 224/45


British 20 mm/70 in Mark IIA Pedestal Mount formerly on the Polish Destroyer Blyskawica
This weapon is now at the Exposition of Navy Museum, Gdynia
Photograph copyrighted by Michal Kopacz


Another view of a British 20 mm, this one on HMCS Prince Henry in a Mark VIIA mounting
Note the safety rail installation
Canada Department of National Defence / Library and Archives Canada Photograph e002852524


British 20 mm in Mark V twin mounting on HMS Starling
IWM photograph A 22088


Post-war use of 20 mm Oerlikon gun manned by the RAF in Aden
IWM photograph RAF-T 5155


Mark 15 Quad Mount
USN Photograph


USN 20 mm Mark 4 Oerlikon Diagram


USN Projectiles of World War II
 Diagonal Stripes represents the body and body walls, small dots represent the tracer elements, dense dots represent the incendiary elements, other dots represent explosive (HE) burster elements.  Explosive, incendiary and tracer elements were loaded in increments, as shown in the above sketches.


Cutaway views of 20 mm ammunition

Page History

28 May 2008 - Benchmark
16 January 2010 - Added picture of HMCS Prince Henry
14 January 2011 - Added cutaway sketch
28 January 2012 - Redid picture of British mounting at Gdynia
28 December 2013 - Added photographs of HMS Starling and RAF gun