| Mk 20 Mod 0 | |
| Origin: | United States |
| Type: | Automatic grenade launcher |
| Is Ranged: | YES |
| Used By: | US Navy |
| Wars: | Vietnam War |
| Manufacturer: | NOS Louisville |
| Weight: | 26 pounds |
| Length: | 27 inches |
| Part Length: | 12 inches |
| Cartridge: | 40x46mm SR |
| Caliber: | 40mm |
| Action: | Blow-forward |
| Rate: | Semi-Automatic 250-275 RPM Full Automatic |
| Velocity: | 250 feet per second |
| Range: | 350m |
| Max Range: | 400m |
| Feed: | 24 round belt |
| Sights: | Iron |
The Mk 20 Mod 0 was a 40mm automatic grenade launcher manufactured by NOS Louisville which was used by the US Navy during the Vietnam War. The Mk 20 was eventually replaced by the Mk 19 Mod 3.
It used a blow-forward mechanism that was previously used on semi-automatic pistols such as the Steyr Mannlicher M1894 and Schwarzlose Model 1908.