Mauser BK-27

The BK 27 (also BK27 or BK-27) (German acronym for Bordkanone, "on-board cannon") is a 27 mm (1.063 in) caliber revolver cannon manufactured by Mauser (now part of Rheinmetall) of Germany. It was developed in the late 1960s for the MRCA (Multi Role Combat Aircraft) program that ultimately became the Panavia Tornado.

The BK 27 is a gas-operated cannon firing a new series of 27×145 mm cartridges with a typical projectile weight of 260 g (9.2 oz), and a total weight for the complete round of 516 g (1.14 lb). Most models use a linked feed system for the ammunition; however, the Eurofighter Typhoon makes use of a specially developed variant of the BK 27 that uses a linkless feed system instead, which is intended to improve reliability.

Design
The Mauser BK 27 is used in the Panavia Tornado, the Alpha Jet, the JAS 39 Gripen, and the Eurofighter Typhoon. At one time the USAF was considering to license its production for the F-35 Lightning II, but instead elected for the GAU-22/A.

Rheinmetall has also developed remote controlled naval versions, the MN 27 GS and the MLG 27 fully automatic naval guns, which are installed on many ships of the German Navy. Ninety-nine MLG 27s have been ordered by the German Navy so far. The cannon is a single-barrel, high performance, breech-cylinder gun operated by a fully automatic electrically fired gas-operated system at a selective rate of 1000 or 1700 rounds per minute(+/− 100 rpm). The Mauser BK 27 utilizes pyrotechnic cocking charges to cycle the action.

The BK27 has a 3-4 times lower nominal fire rate than the M61 Vulcan, but its fire rate is constant throughout firing because the cannon do not need to start spinning the barrel/barrels. As a result, in conjunction with the higher caliber, the Mauser BK 27 fires in the first 0.5 s 4 kg of projectiles in contrast to the 2 kg of the M61 Vulcan which also needs about 25 kW electrical power on the maximum fire rate.

The gun mainly fires mine shells as these have the best effect against aircraft, there are also several types of armor piercing shells like the frangible armour piercing shell named Fap 27 mm x 145 mm ammunition/peb327 (DM103).

Users
Aircraft versions only.
 * Austrian Air Force
 * Bolivian Air Force
 * Brazilian Air Force
 * Cameroon Air Force
 * Canada (Discovery Air Defence Services)
 * Czech Air Force
 * German Air Force
 * Hungarian Air Force
 * Italian Air Force
 * Portuguese Air Force
 * South African Air Force
 * Royal Saudi Air Force
 * Swedish Air Force (under the designation 27 mm automatkanon m/85, 27 mm akan m/85)
 * Spanish Air Force
 * Royal Thai Air Force
 * Royal Air Force
 * Qinetiq