20×110mm USN

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20×110mm USN
TypeAutocannon
Place of origin USA
Service history
In service1950s–present
Used byUnited States Navy Royal New Zealand Air Force
WarsVietnam
Production history
DesignerUnited States Navy
Specifications
Case typeRimless, bottleneck
Bullet diameter19.9 mm (0.78 in)
Neck diameter20.6 mm (0.81 in)
Base diameter29 mm (1.1 in)
Rim diameter29.5 mm (1.16 in)
Case length109.5 mm (4.31 in)
Overall length185 mm (7.3 in)
Primer typeElectric
Maximum pressure600 MPa (87,000 psi)

The 20×110mm USN (also known as 20×110mm US Navy and 20mm Mk-100 Series) was developed by the US Navy after World War II for use in Mk 11 and Mk 12 autocannon. They are called the Mk 100 series as they range from Mk 101 to Mk 109.

It has the same rim diameter as the 20×102mm but a different length and contour. It is not interchangeable with any other 20×110mm cartridge.[1]

Available loads[edit]

Some of the available loads for the 20×110mm USN are as follows:

Name Pressure (PSI) Projectile weight (grains) Projectile Type Muzzle Velocity (fps) Identification
Cartridge, 20mm, High Pressure Test, Mk 101 Mod 0 (USN) Not to exceed 72,500 1700 Inert Not listed Green or blue projectile with brown nose and 1/4 black letters reading "High Pressure Test Round"
Cartridge, 20mm, Low Pressure Test, Mk 102 Mod 0 (USN) Not listed 1700 Inert Not listed Green or blue projectile with brown nose and 1/4 black letters reading "Low Pressure Test Round"
Cartridge, 20mm, High Explosive Incendiary, Mk 105 Mod 0 (USN) Not to exceed 72,500 1700 Inert 3350 Green or blue projectile black lettering or blue projectile with brown nose and black lettering
Cartridge, 20mm, High Explosive Incendiary, Mk 106 Mod 0 & 1 (USN) 60000 1700 ±50 Impact detonating 3350 Unpainted fuze, red and yellow projectile
Cartridge, 20mm, Armor Piercing-Incendiary, Mk 107 Mod 0 (USN) 60000 1700 ±50 Armour Piercing Incendiary 3350 No fuze, Nose of projectile blue or brown with red band. Body of projectile black with white lettering.
Cartridge, 20mm, Armor Piercing-Tracer, Mk 108 Mod 0 (USN) 60000 1700 ±50 Armour Piercing Tracer 3350 No fuze. Hollow windshield. Brown or yellow nose, body of projectile black with white lettering.

There is also a Cartridge, 20mm, Dummy, Mk 103 Mod 0 (USN) which is an inert round. It has an empty primer pocket and holes in the case or a plugged primer pocket. It may be empty or filled with inert material. The projectile is usually brass or bronze plated.[2]

References[edit]

  1. ^ Albert Watson III (1985). Small Calibre Ammunition Identification Guide, DST-1160G-514-82-VOL 2-CHG 1(Volume 2: 20mm to 40mm Cartridges.). Defence Intelligence Agency.
  2. ^ Frank Barnes (2009). Layne Simpson, ed. Cartridges of the World (12th ed.). USA: Gun Digest Books. pp. 512–513.