The 3 cm MK 303 Flak and twin-mounted 3 cm MK 303 Flakzwilling (M44) were experimental 30 mm anti-aircraft guns developed in Nazi Germany. They fired the powerful 30x210mm round and only 222 were produced.[1] The gun was to be installed on Type XXI submarines as AA defense[3] and its use as AA defense replacing 2 cm Flak and 3.7 cm Flak weapons was also considered. The use of 3 cm M.K. 303 Flakzwilling on Flakpanzer IV "Kugelblitz" was considered, but rejected. The development began in late 1941[1] and production started in late 1944.
| 3 cm MK 303 (Br) | |
|---|---|
3cm MK 303 Flakzwilling, two 3 cm MK 303 in the twin mount | |
| Type | Anti-aircraft cannon |
| Place of origin | Nazi Germany |
| Service history | |
| In service | unknown |
| Used by | Nazi Germany |
| Wars | World War II |
| Production history | |
| Manufacturer | Krieghoff[1] |
| Produced | 1944–1945 |
| No. built | 222 (32 in 1944 and 190 in 1945)[1] |
| Variants | 3 cm Flakzwilling MK 303 (Br) |
| Specifications | |
| Mass | 185 kg (408 lbs)[2] |
| Length | 3.145 m (10 ft 3.8 in) |
| Barrel length | 2.2 m (7 ft 3 in) L/73 |
| Shell | 30×210mm |
| Caliber | 30 mm (1.18 in) |
| Elevation | -10°to ±85° |
| Traverse | 360° |
| Rate of fire | 400 rpm (cyclic) |
| Muzzle velocity | 1100 m/s (3,609 ft/s) M-Schos 900 m/s (2,953 ft/s) HE 950 m/s (3,117 ft/s) AP/HE[2] |
| Feed system | 15 cartridge clip |

In the 50s, the MK 303 was produced in Czechoslovakia under the designation M53, with the clip feed replaced by a 10-round box magazine.[1] It was also used as armament of SPAAG M53/59 Praga.
German artillery of World War II | |
|---|---|
| Tank guns |
|
| Anti-tank guns |
|
| Infantry and mountain guns |
|
| Recoilless guns |
|
| Mortars |
|
| Heavy mortars |
|
| Rocket artillery |
|
| Field, medium and heavy guns |
|
| Superheavy and siege artillery |
|
| Railroad artillery |
|
| Naval artillery |
|
| Anti-aircraft guns | |
| Demolition charges |
|