Description
Inert 20mm Mark 3 Round for the 20x110mm Oerlikon Cannon
Item Overview
This inert 20mm Mark 3 round represents fixed ammunition used with the 20x110mm Oerlikon automatic cannon. It consists of a Mark 3 projectile assembled with an Oerlikon-pattern cartridge case. The round has been confirmed inert and contains no live primer, propellant, explosive, incendiary mixture, or other energetic material. Its complete profile makes it an impressive display piece for collections covering World War II naval weapons, automatic cannon ammunition, and U.S. military history.
Identification and Features
The Mark 3 designation identifies the projectile rather than the cartridge case. U.S. Navy records list Mark 3 projectiles in high-explosive, high-explosive incendiary, and blind-loaded-and-plugged configurations. The exact original loading represented by this example has not been specified. Its 20x110mm Oerlikon cartridge family can be recognized by the reduced-diameter extractor lip at the case head. This feature gives the cartridge its common 20x110mm RB designation, with “RB” meaning rebated rim.
- Item type: Complete inert automatic-cannon round
- Caliber: 20mm
- Cartridge family: 20x110mm Oerlikon
- Alternative designation: 20x110mm RB
- Projectile designation: Mark 3
- Original projectile family: HE, HE-I, or blind-loaded and plugged
- Ammunition form: Fixed cartridge
- Associated weapon: 20mm Oerlikon automatic cannon
- Current status: Completely inert and non-firing
- Included: One inert 20mm Mark 3 round
Mark 3 Service Configurations
The Mark 3 projectile was produced in many modification numbers, with wartime manuals listing Mods 1 through 64. Many of these Mod numbers identified products made under different contracts rather than major changes in performance. High-explosive versions carried either tetryl or pentolite, while high-explosive incendiary versions combined an incendiary mixture with an explosive charge. The blind-loaded-and-plugged version used inert material and a dummy nose cap for training. The historic paint colors included white or yellow for HE, red or light pink for HE-I, and dark gray-green for blind-loaded ammunition. Paint should not be used by itself to identify a surviving round because many examples have faded, weathered, or been repainted.
Original Service Function
The live Mark 3 HE projectile was designed to burst when it struck an aircraft or another target. The HE-I version added an incendiary effect that could damage fuel, fabric, and other flammable aircraft parts. These Mark 3 types did not contain a tracer. Live HE and HE-I projectiles were normally fitted with a Mark 26-series impact fuze. Blind-loaded-and-plugged rounds copied the general weight and handling of service ammunition without a working explosive charge. This example has been deactivated and cannot perform any original firing, impact, explosive, or incendiary function.
Cartridge and Weapon Application
The Oerlikon used fixed ammunition, meaning the projectile, cartridge case, primer, and propellant formed one complete unit for loading. The cartridges were supplied to the weapon through a removable spiral drum mounted above the receiver. Mark 3 projectiles could be assembled with different approved Oerlikon cartridge cases, including brass and steel versions. A Mark 3 steel case was one possible case type, but the Mark 3 marking on this item identifies the projectile and does not establish the case Mark or material. The 20x110mm Oerlikon round must also be distinguished from the separate 20x110mm Hispano-Suiza ammunition family, which used a different case-head design and was not interchangeable.
Original Specifications
U.S. Navy references give the original Mark 3 projectile a length of approximately 3.275 inches with its nose fuze and 2.625 inches without the fuze. A loaded service projectile weighed about 0.271 pound. Oerlikon cartridge cases were approximately 4.343 inches long with a base diameter near 0.827 inch. A complete service round could measure up to about 7.18 inches long and weigh approximately 8.5 ounces. The dimensions and weight of this inert example may vary because its internal components and original loading have been removed or replaced.
Weapon System History
The Oerlikon cannon developed from the German Becker automatic cannon created during World War I. Its design passed through the Swiss company SEMAG before Oerlikon continued development during the 1920s and 1930s. The powerful 20x110mm rebated-rim cartridge helped make the weapon suitable for antiaircraft and naval defense. The U.S. Navy selected the Oerlikon before America entered World War II and placed improved versions into large-scale production. American models included the 20mm Oerlikon Guns Marks 2, 3, and 4, with the Mark 4 becoming the most common U.S.-made version.
History of Use
During World War II, the 20mm Oerlikon became one of the most common close-range antiaircraft guns in Allied naval service. It was installed on aircraft carriers, battleships, cruisers, destroyers, submarines, patrol craft, landing vessels, auxiliary ships, and armed merchant vessels. Gun crews used it against low-flying aircraft and other close targets in the Atlantic, Mediterranean, and Pacific theaters. Its quick handling and high rate of fire gave ships more defensive power than the heavy machine guns it often replaced. Heavier 40mm weapons became more important against large aircraft and kamikaze attacks later in the war, but the Oerlikon remained an important part of shipboard defense and continued in service after 1945.
Historical Significance
This inert Mark 3 round represents the ammunition used by thousands of Allied sailors responsible for close-range defense during World War II. The complete cartridge shows the distinctive proportions and rebated case head of the 20x110mm Oerlikon family. It is also a useful example of the varied projectile loadings developed for the same weapon system. No specific manufacturer, production date, ammunition lot, case Mark, fuze model, ship, or combat history is claimed unless established by markings on the item.
Condition
This is an inert surplus display round. It may show scratches, dents, worn paint, oxidation, corrosion, discoloration, tool marks, or other signs of age, storage, deactivation, and previous handling. Markings, cartridge-case material, finish, projectile color, and minor construction details may vary. The round contains no live energetic components and is not intended for firing or placement in a functioning weapon. This listing includes one inert 20mm Mark 3 round only. The Oerlikon cannon, drum magazine, ammunition container, and other accessories are not included unless specifically stated.
Ideal For
This inert round is well suited for collections and exhibits covering naval antiaircraft weapons, World War II ammunition, automatic cannons, and military manufacturing. Its complete profile displays well beside Oerlikon cartridge cases, projectiles, magazines, manuals, ship models, and other inert naval ordnance.
- 20mm ammunition collections
- 20x110mm Oerlikon displays
- World War II naval exhibits
- Automatic-cannon collections
- Inert ordnance displays
- Military museums and educational programs
- Veterans’ organizations and military-history rooms
Approx length 7.18", Approx width .83", Approx height .83", Approx weight .53 lbs.
Pictures are stock images of our inventory. Unless otherwise noted, you will not be receiving the exact item shown in the pictures. The pictures are representative of the item’s general condition. The item you receive might be slightly better, or worse, condition than was shown in the pictures.
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