3 cm MK 303 Flak

{{Short description|German anti-aircraft gun}}

{{Infobox weapon

| name = 3 cm MK 303 (Br)

| image = 3_cm_flak_303_twin_ubts.jpg

| caption = 3cm MK 303 Flakzwilling, two 3 cm MK 303 in the twin mount

| origin = Nazi Germany

| type = Anti-aircraft cannon

| is_ranged = yes

| is_artillery = yes

| service = unknown

| used_by = Nazi Germany

| wars = World War II

| designer =

| design_date =

| manufacturer = Krieghoff{{Cite web|url=http://alternathistory.com/aviapushki-krighoffa-mg-301-mk-303/|title=Авиапушки Кригхоффа. MG 301, MK 303|date=December 28, 2015|access-date=July 14, 2019|archive-date=July 14, 2019|archive-url=https://web.archive.org/web/20190714194253/http://alternathistory.com/aviapushki-krighoffa-mg-301-mk-303/|url-status=dead}}

| production_date = 1944–1945

| number = 222 (32 in 1944 and 190 in 1945)

| variants = 3 cm Flakzwilling MK 303 (Br)

| weight = 185 kg (408 lbs){{Cite web|url=https://www.armedconflicts.com/3-cm-M-K-303-Br-3-cm-Flakzwilling-M-K-303-Br-t38139|title=3 cm M.K.303 (Br) / 3 cm Flakzwilling M.K.303 (Br) : Germany (DEU)|website=armedconflicts.com|date=26 January 2006 }}

| length = {{convert|3.145|m|ftin|abbr=on}}

| part_length = {{convert|2.2|m|ftin|abbr=on}} L/73

| width =

| height =

| crew =

| cartridge = 30×210mm

| caliber = 30 mm (1.18 in)

| action =

| rate = 400 rpm (cyclic)

| 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

| range =

| feed = 15 cartridge clip

| sights =

| breech =

| recoil =

| carriage =

| elevation = -10°to ±85°

| traverse = 360°

}}

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. The gun was to be installed on Type XXI submarines as AA defense{{Cite web|url=http://www.ww2technik.de/dsub_geschuetze.htm|title=dsub geschütze|website=www.ww2technik.de}} 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 and production started in late 1944.