20×110mm USN
| 20×110mm USN | |
|---|---|
| Type | |
| Place of origin |
 USA
|
| Service history | |
| In service | 1950s–present |
| Used by | Royal New Zealand Air Force |
| Wars | Vietnam |
| Production history | |
| Designer | United States Navy |
| Specifications | |
| Case type | Rimless, bottleneck |
| Bullet diameter | 19.9 mm (0.78 in) |
| Neck diameter | 20.6 mm (0.81 in) |
| Base diameter | 29 mm (1.1 in) |
| Rim diameter | 29.5 mm (1.16 in) |
| Case length | 109.5 mm (4.31 in) |
| Overall length | 185 mm (7.3 in) |
| Primer type | Electric |
| Maximum pressure | 600 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 . 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.
Some of the available loads for the 20×110mm USN are as follows:
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.
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