# Mauser BK-27
The **Mauser BK-27** (Bordkanone 27, German for "on-board cannon 27mm") is a 27mm gas-operated revolver autocannon developed by Mauser-Werke of Oberndorf, Germany, for fighter aircraft and later adapted to remote-controlled naval mounts. It fires the 27×145mm Mauser cartridge, of which it is the only chambered autocannon, at a selectable rate of 1,000 or 1,700 rounds per minute, and more than 3,000 systems have been sold.[1](https://weaponsystems.net/system/880-27mm%2BMauser%2BBK-27) • [2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf) It is the standard gun of the [Panavia Tornado](https://www.edgepedia.org/panavia-tornado) and [Eurofighter Typhoon](https://www.edgepedia.org/eurofighter-typhoon), is fitted to certain Saab Gripen versions, and serves in the [German Navy](https://www.edgepedia.org/german-navy) as the MLG 27.[2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf)
| Key fact | Detail |
|---|---|
| Type | Single-barrel, gas-operated, electrically primed revolver cannon; Bordkanone = "on-board cannon"[3](https://web.archive.org/web/20170626182500/https:/www.raf.mod.uk/equipment/mauser-cannon.cfm) • [1](https://weaponsystems.net/system/880-27mm%2BMauser%2BBK-27) |
| Cartridge | 27×145mm Mauser; complete round 516 g, full-caliber projectile 260 g[2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf) |
| Rate of fire | Selectable 1,000 or 1,700 rounds per minute, reached almost from the first round[3](https://web.archive.org/web/20170626182500/https:/www.raf.mod.uk/equipment/mauser-cannon.cfm) |
| Muzzle velocity | 1,000 m/s full-caliber, 1,100 m/s sub-caliber ammunition (manufacturer); 1,025 m/s quoted for the Eurofighter variant[2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf) • [4](http://gotech.at/mauser_bk27.htm) |
| Weight and size | About 100 kg including barrel (102.5 kg in one listing); barrel 1.4 m, total length 2.3 m[5](https://eurofighter.airpower.at/bew-bordkanone.htm) • [4](http://gotech.at/mauser_bk27.htm) |
| Production | More than 3,000 systems sold; qualified for Eurofighter, Gripen, Tornado and the German Navy[2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf) |
| F126 order | November 2022: eight MLG27-4.0 systems for Germany's F126 frigates, two per ship[6](https://www.rheinmetall.com/en/media/news-watch/news/2022/2022-11-17_next-generation-gun-systems) |
## Design and operating principle
The BK-27 is a revolver cannon: a single barrel paired with a rotating breech cylinder that carries the chamber. The [Royal Air Force](https://www.edgepedia.org/royal-air-force) describes it as a single-barrel, breech-cylinder gun operated by a fully automatic, electrically fired gas-operated system.[3](https://web.archive.org/web/20170626182500/https:/www.raf.mod.uk/equipment/mauser-cannon.cfm) The cartridge is ignited electrically rather than by a firing pin.[7](https://www.saairforce.co.za/the-airforce/weapons/32/mauser-bk-27-27mm-cannon)
The revolver layout's practical advantage is time-to-rate. Because the cylinder is already spinning up with the first shot, the gun reaches its full 1,700-rounds-per-minute rate almost from the first round, which the RAF cites as a main strength against fast-moving targets; a Gatling-type rotary cannon must spin its barrel cluster up to speed before it delivers a comparable burst.[3](https://web.archive.org/web/20170626182500/https:/www.raf.mod.uk/equipment/mauser-cannon.cfm) • [1](https://weaponsystems.net/system/880-27mm%2BMauser%2BBK-27) For very short burst lengths this gives the revolver an edge over gatling-type autocannons of similar caliber.[1](https://weaponsystems.net/system/880-27mm%2BMauser%2BBK-27)
Ammunition is fed through linked belts or, in the Eurofighter, through a linkless conveyor-belt feed described as the first such system for a revolver gun; linkless systems are less prone to stoppage and use less space, reducing installation volume by about 60 percent in the Eurofighter fit.[7](https://www.saairforce.co.za/the-airforce/weapons/32/mauser-bk-27-27mm-cannon) • [4](http://gotech.at/mauser_bk27.htm) The RAF installation adds a floating buffer system that imposes very small recoil and vibration loads on the airframe, and ducts spent cases and links into a collection bay with ram-air purging.[3](https://web.archive.org/web/20170626182500/https:/www.raf.mod.uk/equipment/mauser-cannon.cfm)
## Development history
The linked-feed version became a standard weapon on the multi-role Tornado.[9](https://www.upi.com/Defense-News/2016/03/01/Saab-orders-Mauser-BK-27-cannons-for-its-Gripen-fighters/5361456853595/)
When the Eurofighter requirement was defined, a mid-1980s performance evaluation of on-board cannons found no alternative to the BK 27, and variants of the gun were selected for the Eurofighter 2000.[4](http://gotech.at/mauser_bk27.htm) • [10](https://boeing.mediaroom.com/1998-07-29-Boeing-Mauser-Primex-Team-for-27mm-Cannon-for-JSF) The gun then made two bids for the American Joint Strike Fighter. In July 1998 Boeing, Mauser, and Primex teamed to offer a 27mm gas-operated automatic revolver gun based on the BK 27.[10](https://boeing.mediaroom.com/1998-07-29-Boeing-Mauser-Primex-Team-for-27mm-Cannon-for-JSF) In April 1999 [Lockheed Martin](https://www.edgepedia.org/lockheed-martin) baselined the Mauser 27mm cannon for its JSF bid while also considering the General Dynamics GAU-12 25mm three-barrel [Gatling gun](https://www.edgepedia.org/gatling-gun), and Boeing officials said they were "impressed with the Mauser gun's low recoil loads and blast control".[11](https://www.flightglobal.com/fixed-wing/1999/04/lockheed-martin-favours-german-cannon-for-jsf/) Boeing selected an Advanced 27mm Aircraft Cannon, firing electrically primed ammunition at 1,800 shots per minute, as the basis for its JSF gun system, developed with Mauser-Werke Oberndorf, Primex Technologies, and [Western Design](https://www.edgepedia.org/western-design); had it been selected, Boeing's Mesa, Arizona operation would have produced up to 3,000 cannons under license.[12](https://www.globalsecurity.org/military/library/news/1999/04/mil-990428-boeing01.htm) • [11](https://www.flightglobal.com/fixed-wing/1999/04/lockheed-martin-favours-german-cannon-for-jsf/) A Boeing demonstration in April 1999 marked the first US showing of the 27mm linear linkless feed and case recovery system.[13](https://boeing.mediaroom.com/1999-04-07-Boeing-Demonstrates-27MM-Cannon-Proposed-For-JSF)
## Ammunition
The BK-27 fires the 27×145mm Mauser cartridge. The complete round weighs 516 g without belt link and the full-caliber projectile 260 g.[2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf) The gun can fire several types of high-explosive and armor-piercing rounds, and all types share the same internal and external ballistic properties, allowing belts with mixed ammunition for flexibility.[3](https://web.archive.org/web/20170626182500/https:/www.raf.mod.uk/equipment/mauser-cannon.cfm) • [7](https://www.saairforce.co.za/the-airforce/weapons/32/mauser-bk-27-27mm-cannon) In naval service the round of note is the FAPDS (frangible armor-piercing discarding sabot), a sub-caliber projectile of 0.260 kg in a 0.516 kg complete round at about 1,100 m/s muzzle velocity.[8](https://www.navweaps.com/Weapons/WNGER_27mm-145_mlg27.php)
## Platform installations and service use
**Tornado.** The Tornado IDS carries two BK-27 guns and the air-defense ADV variant one; the ECR electronic-warfare variant and some reconnaissance conversions carry none.[1](https://weaponsystems.net/system/880-27mm%2BMauser%2BBK-27) The Royal Air Force fits the cannon to the Tornado GR4 and the Typhoon for air-to-air or air-to-ground firing, with targeting through the head-up display and a continuously compacted impact-line firing predictor.[3](https://web.archive.org/web/20170626182500/https:/www.raf.mod.uk/equipment/mauser-cannon.cfm)
**Eurofighter Typhoon.** Each Typhoon carries a single BK 27 with a 150-round magazine; the barrel is 1.4 m long, total gun length 2.3 m, and weight excluding ammunition 100 kg, with the rate of fire pilot-selectable from 1,700 down to 1,000 rounds per minute.[5](https://eurofighter.airpower.at/bew-bordkanone.htm) On British Eurofighters the gun was fitted only in production lot 1, one per aircraft from Block 1 in 2003.[5](https://eurofighter.airpower.at/bew-bordkanone.htm)
**Gripen.** The BK-27 is fitted to the Saab Gripen, but only the single-seat JAS-39C and JAS-39E versions carry the cannon, with 120 rounds; a Gripen E prototype test flight fired its internal 27×145mm gun in a documented trial.[14](https://aeroflap.com.br/en/video-fluen-and-makes-test-flight-firing-27mm-cannon/) In March 2016 [Rheinmetall](https://www.edgepedia.org/rheinmetall) was selected to supply BK-27 cannons with a newly developed linkless ammunition feeding system for 88 Gripen NG fighters for the Swedish and Brazilian air forces, with deliveries to Saab between 2017 and 2025; the contract also covered service support, spare parts, and associated ammunition.[9](https://www.upi.com/Defense-News/2016/03/01/Saab-orders-Mauser-BK-27-cannons-for-its-Gripen-fighters/5361456853595/) • [15](https://www.airforce-technology.com/news/newsrheinmetall-to-supply-automatic-cannon-for-swedish-and-brazilian-gripen-ng-4827317/)
**Other fits.** The cannon has been adapted to the Alpha Jet, and Rheinmetall lists C-295-based gunships among typical installations.[16](https://www.deagel.com/Cannons%20&%20Gear/BK%2027/a001599) • [2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf)
## Naval and land applications: the MLG 27
The MLG 27 is the navalized version of the aircraft gun, designed by Mauser-Werke Oberndorf Waffensysteme GmbH, then a Rheinmetall subsidiary, to replace older 20mm and 40mm naval guns; its mounting requires no deck penetration. It entered service in 2003, and 83 weapons had been ordered by the German Navy at the time of that record.[8](https://www.navweaps.com/Weapons/WNGER_27mm-145_mlg27.php) The mount carries 90 rounds and offers left- or right-hand linkless feed with case recovery, at a cyclic rate of 1,700 ±100 rounds per minute.[8](https://www.navweaps.com/Weapons/WNGER_27mm-145_mlg27.php) Fire control from STN Atlas Elektronik combines a thermal imager, TV camera, laser range finder, and automatic video target tracking, operable remotely or by joystick.[8](https://www.navweaps.com/Weapons/WNGER_27mm-145_mlg27.php) Effective range is 2,500 m against small, highly agile surface targets, helicopters, and subsonic aircraft, with a maximum of 4,000 m against on-shore targets and warships.[8](https://www.navweaps.com/Weapons/WNGER_27mm-145_mlg27.php) Over 100 MLG 27 mounts have been produced, a notable shift for a weapon that had been purely an aircraft gun for decades.[1](https://weaponsystems.net/system/880-27mm%2BMauser%2BBK-27)
Export followed. On 29 June 2006 the US Navy awarded Rheinmetall a $43 million contract for 12 MLG 27 systems with test ammunition, spares, logistics, engineering support, and training, for MKV-C fast-interceptor boats acquired by Kuwait under a [Foreign Military Sales](https://www.edgepedia.org/foreign-military-sales) program.[16](https://www.deagel.com/Cannons%20&%20Gear/BK%2027/a001599) Operator counts in one equipment database list Germany with 95 active guns, Kuwait 12, Sweden 8, and Angola 6 planned; the German figure differs from NavWeaps' 83.[16](https://www.deagel.com/Cannons%20&%20Gear/BK%2027/a001599)
The line continues to develop. In November 2022 Rheinmetall received an order from the Dutch shipbuilder Damen Naval to supply eight MLG27-4.0 defense systems for Germany's F126-class frigates, two per vessel, in an order worth a two-digit million-euro figure.[6](https://www.rheinmetall.com/en/media/news-watch/news/2022/2022-11-17_next-generation-gun-systems) The remotely controlled MLG27-4.0, part of the SeaSnake remote weapon station family, is built around the BK-27M revolver gun chambered in 27×145B mm, which can fire single shots, adjustable bursts, or a sustained rate of up to 1,700 rounds per minute; its sight adds day and thermal channels, a laser rangefinder, automatic target tracking, and engagement at WGS-84 target coordinates. The predecessor MLG27 serves on Germany's F125 frigates.[6](https://www.rheinmetall.com/en/media/news-watch/news/2022/2022-11-17_next-generation-gun-systems) • [17](https://euro-sd.com/2022/11/news/28289/rheinmetall-to-equip-f126-frigates-with-27-mm-automatic-cannons/)
## How it compares with other fighter guns
Within Rheinmetall's own medium-caliber portfolio, the 20mm KAE fires at 1,000 rounds per minute, the 25mm KBA at 600, and the 30mm KCA at 1,350, against the BK27's 1,700.[2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf) Against the [GAU-12](https://www.edgepedia.org/gau-12-equalizer) 25mm Gatling considered for the JSF, the BK-27's case rested on lower recoil loads and blast control, and near-instant time-to-rate for short bursts.[11](https://www.flightglobal.com/fixed-wing/1999/04/lockheed-martin-favours-german-cannon-for-jsf/) • [1](https://weaponsystems.net/system/880-27mm%2BMauser%2BBK-27)
## By the numbers
Consolidated figures, with the discrepancies stated: rate of fire is 1,700 rounds per minute in Rheinmetall's datasheet as a single figure, while the RAF, airpower.at and weaponsystems.net describe a selectable 1,000 or 1,700 rounds per minute.[2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf) • [3](https://web.archive.org/web/20170626182500/https:/www.raf.mod.uk/equipment/mauser-cannon.cfm) • [5](https://eurofighter.airpower.at/bew-bordkanone.htm) [Muzzle velocity](https://www.edgepedia.org/muzzle-velocity) depends on ammunition: 1,000 m/s with full-caliber and 1,100 m/s with sub-caliber rounds per the manufacturer, 1,025 m/s quoted for the Eurofighter variant, and "just over 1 km/s" in the [South African Air Force](https://www.edgepedia.org/south-african-air-force) summary.[2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf) • [4](http://gotech.at/mauser_bk27.htm) • [7](https://www.saairforce.co.za/the-airforce/weapons/32/mauser-bk-27-27mm-cannon) Weight is about 100 kg including barrel, 102.5 kg in the Eurofighter listing and 102 kg in the manufacturer's table.[7](https://www.saairforce.co.za/the-airforce/weapons/32/mauser-bk-27-27mm-cannon) • [4](http://gotech.at/mauser_bk27.htm) • [2](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf) The Eurofighter variant's muzzle energy is given as 136,600 Nm.[4](http://gotech.at/mauser_bk27.htm) For the naval mount, effective range is 2,500 m against surface targets, helicopters and subsonic aircraft and 4,000 m maximum against on-shore targets and warships.[8](https://www.navweaps.com/Weapons/WNGER_27mm-145_mlg27.php)
## Manufacture and outlook
Production and support sit with Rheinmetall Waffe Munition GmbH of Unterlüß, which builds the BK-27M under the Mauser brand Rheinmetall owns.[6](https://www.rheinmetall.com/en/media/news-watch/news/2022/2022-11-17_next-generation-gun-systems) The documented programs include the scheduled 2017–2025 delivery window for 88 Gripen NG gun systems with linkless feed to Saab and the November 2022 F126 order for eight MLG27-4.0 mounts with an option for four more.[9](https://www.upi.com/Defense-News/2016/03/01/Saab-orders-Mauser-BK-27-cannons-for-its-Gripen-fighters/5361456853595/) • [17](https://euro-sd.com/2022/11/news/28289/rheinmetall-to-equip-f126-frigates-with-27-mm-automatic-cannons/)
## References
1. [27mm Mauser BK-27, Weaponsystems.net](https://weaponsystems.net/system/880-27mm%2BMauser%2BBK-27)
2. [Rheinmetall – Leadership in cannon design (medium calibre portfolio brochure)](https://www.rheinmetall.com/Rheinmetall%20Group/brochure-download/Weapon-Ammunition/B226e0620-Rheinmetall-Leadership-in-cannon-design-medium-calibre-portfolio.pdf)
3. [Royal Air Force – Mauser Cannon (archived)](https://web.archive.org/web/20170626182500/https:/www.raf.mod.uk/equipment/mauser-cannon.cfm)
4. [Die Mauser BK 27 für den Eurofighter, gotech.at](http://gotech.at/mauser_bk27.htm)
5. [Eurofighter Typhoon – Bordkanone BK 27, airpower.at](https://eurofighter.airpower.at/bew-bordkanone.htm)
6. [Next-generation gun systems MLG27-4.0 for German frigates, Rheinmetall press release, 17 November 2022](https://www.rheinmetall.com/en/media/news-watch/news/2022/2022-11-17_next-generation-gun-systems)
7. [South African Air Force – Mauser BK 27 27mm Cannon](https://www.saairforce.co.za/the-airforce/weapons/32/mauser-bk-27-27mm-cannon)
8. [Germany 27 mm/145 MLG 27, NavWeaps](https://www.navweaps.com/Weapons/WNGER_27mm-145_mlg27.php)
9. [Saab orders Mauser BK-27 cannons for its Gripen fighters, UPI, 1 March 2016](https://www.upi.com/Defense-News/2016/03/01/Saab-orders-Mauser-BK-27-cannons-for-its-Gripen-fighters/5361456853595/)
10. [Boeing/Mauser/Primex Team for 27mm Cannon for JSF, Boeing press release, 29 July 1998](https://boeing.mediaroom.com/1998-07-29-Boeing-Mauser-Primex-Team-for-27mm-Cannon-for-JSF)
11. [Lockheed Martin favours German cannon for JSF, FlightGlobal, April 1999](https://www.flightglobal.com/fixed-wing/1999/04/lockheed-martin-favours-german-cannon-for-jsf/)
12. [Boeing To Use Advanced 27MM Cannon As Basis For JSF Design, via GlobalSecurity, April 1999](https://www.globalsecurity.org/military/library/news/1999/04/mil-990428-boeing01.htm)
13. [Boeing Demonstrates 27MM Cannon Proposed For JSF, Boeing press release, 7 April 1999](https://boeing.mediaroom.com/1999-04-07-Boeing-Demonstrates-27MM-Cannon-Proposed-For-JSF)
14. [Gripen E makes test flight firing 27mm cannon, Aeroflap](https://aeroflap.com.br/en/video-fluen-and-makes-test-flight-firing-27mm-cannon/)
15. [Rheinmetall to supply automatic cannon for Swedish and Brazilian Gripen NG, Airforce Technology](https://www.airforce-technology.com/news/newsrheinmetall-to-supply-automatic-cannon-for-swedish-and-brazilian-gripen-ng-4827317/)
16. [BK 27 / MLG 27, Deagel](https://www.deagel.com/Cannons%20&%20Gear/BK%2027/a001599)
17. [Rheinmetall to Equip F126 Frigates with 27 mm Automatic Cannons, European Security & Defence, November 2022](https://euro-sd.com/2022/11/news/28289/rheinmetall-to-equip-f126-frigates-with-27-mm-automatic-cannons/)
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*Topic: Encyclopedia › Technology and the built world › Engineering and manufacturing › Artillery*
*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026; Oct 25, 2026 · Last review: Oct 15, 2026*
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