Recent from talks
Nothing was collected or created yet.
Mk44 Bushmaster II
View on Wikipedia
The Mk44 Bushmaster II is a 30 mm chain gun manufactured by Northrop Grumman. It is a derivative of the 25 mm M242 Bushmaster, and uses 70% of the same parts as the M242 while increasing the firepower by as much as 50% with the 20% increase in caliber size. The barrel is chromium-plated for extended life. The gun uses standard GAU-8 Avenger ammunition that is available in API (Armor-Piercing Incendiary), HEI (High-Explosive Incendiary) and APFSDS-T (Armor-Piercing Fin-Stabilized Discarding Sabot-Tracer) variants.
Key Information
The gun can be converted to a caliber of 40×180 mm, which involves changing the barrel and a few key parts, to use the SuperShot 40 cartridge. It can also be converted to use the 30×170 mm RARDEN cartridge.
History
[edit]The Bushmaster II is the standard primary armament of the Bionix-II AFV currently in service with the Singapore Army, the KTO Rosomak in Polish service, and the CV90 AFVs in Finnish, Norwegian and Swiss service. Although the United States Air Force selected this cannon to replace the 25 mm GAU-12 Equalizer and Bofors 40 mm Automatic Gun L/60 guns on its fleet of AC-130U gunships in 2007, this plan was later canceled.[1] The United States Marine Corps' cancelled Expeditionary Fighting Vehicle, was expected to be armed with this cannon as well. Some United States Navy vessels, such as the new San Antonio-class amphibious transport dock are armed with the Bushmaster II for surface threat defense.
The Bushmaster II cannon is used in the DS30M Mark 2 Automated Small Calibre Gun (ASCG) point defense system that is fitted to the Royal Navy's Type 23 frigates.[2]
The Bushmaster II cannon is also used in the Turkish made Aselsan SMASH stabilized weapon station.[3]
The USAF had experimented with installing Bushmaster II cannons on their AC-130U gunships in place of the GAU-12 and Bofors 40 mm cannons. On 11 August 2008, the effort was canceled because of problems with the Bushmaster's accuracy in tests "at the altitude we were employing it." There were also schedule considerations that drove the decision.[4] On 9 July 2012, the Air Force type classified a new version of the Bushmaster called the GAU-23/A. The cannon will be used on the AC-130W and the AC-130J gunships.[5]

The U.S. Navy uses the Mk44 Bushmaster II in the Mk 46 Mod 2 Gun Weapon System (GWS). The GWS is produced by General Dynamics to give warships protection against small, high-speed surface craft. A Mk 46 turret consists of the 30 mm chain gun, a forward looking infrared (FLIR) sensor, a low light television camera, and a laser rangefinder. The guns fire at 200 rounds per minute and are fed by a 400-round magazine through 200-round dual feeds. Effective range is 2,200 yd (2,000 m) for full-caliber high-explosive or armor-piercing ammunition, which can be extended when using sub-caliber rounds. The Mk 46 GWS is permanently installed on the San Antonio-class amphibious transport dock and can be installed on Freedom and Independence-class littoral combat ships as part of the surface warfare (SuW) package.[6][7] In 2012, the Navy decided to replace the Mk 110 57 mm cannons on Zumwalt-class destroyers with the Mk 46 GWS.[8]
Orbital ATK developed a modified version of the Bushmaster II, known as the Mk44 STRETCH, which can fire the 30x173 mm Mk310 PABM-T airburst round.[9][10]
In January 2020, Northrop Grumman revealed the development of proximity airburst rounds for the LCS' 30 mm gun modules to destroy small unmanned aerial vehicles (UAVs). Since the modules feature dual feeders, different types of rounds could be fed for different targets.[11]
In October 2023, the UK announced it would be delivering the Terrahawk Paladin to Ukraine as part of assistance during the Russian invasion of Ukraine. The Terrahawk Paladin is made by MSI Defence Systems (MSI-DS) as a land-based version of the Seahawk. It is a static Very Short-Range Air Defense (VSHORAD) Counter Unmanned Aerial Systems (C-UAS) system that can be deployed off a truck. The system combines radars, EO/IR cameras, and laser rangefinders with a 30 mm Mk44 Bushmaster II chain gun with 240 rounds of airburst munitions capable of engaging small UAS out to 2 km (1.2 mi).[12][13][14]
XM813
[edit]The XM813 Bushmaster is based on the Mk44 and is offered as an upgrade for U.S. Army M1126 Stryker (adopted as the M1296 Dragoon) and M2 Bradley vehicles, as well as having been a contender to be the primary armament of the Ground Combat Vehicle. The improvements include a 25.4 mm (1.00 in) longer barrel, integral mount to increase first round hit probability by up to 10%, a dual recoil system to enhance accuracy to help cope with future hotter propellants, and a Meggitt linkless dual feed ammunition system.[15] The 30 mm chain gun can fire Mk310 Programmable Air Burst Munition rounds to attack targets in defilade. The United States Army Research, Development and Engineering Command helped enhance the XM813 mainly for safety and turret integration. By changing five parts, the gun caliber can be increased to 40 mm. As of November 2013, the XM813 was being tested at Aberdeen Proving Ground over three months to ensure reliability levels of 40,000 mean rounds between failures. Long-term plans are to equip vehicles with the Bushmaster III 35mm/50mm cannon.[16][17]
The XM813 was demonstrated in September 2014 at the ARDEC Digital Multi-Purpose Range Complex. The gun was mounted on a Bradley Fighting Vehicle and fired at targets up to 1,500 metres (0.93 mi) away. An enhanced fire control system improves long-range accuracy to kill targets with fewer bursts, sometimes as few as two or three rounds instead of 10. The XM813 30 mm cannon is intended to replace the M242 Bushmaster 25 mm chain gun, and can be mounted on vehicles other than the Bradley. Two capabilities not demonstrated were its linkless ammunition with airburst capabilities; airburst rounds increase lethality by enabling engagement of targets in defilade when they would otherwise only be suppressed by fire.[18]
In early 2015, the U.S. Army approved an upgrade for 81 Stryker vehicles of a Stryker Brigade Combat Team deployed in Europe to be upgunned with the Mk44 30 mm Bushmaster cannon to increase their lethality against other light armored vehicles used by Russia in the theater.[19] The cannons will be installed by 2018, and may be the first step in adding the Bushmaster to the entire active fleet of about 1,000 Strykers;[20] the XM813 variant will be used with the Strykers.[21] The XM813 has a demonstrated firing ability out to 3,000 metres (1.9 mi) for precision firing, nearly twice as far as the M2 12.7 mm caliber machine gun that has a maximum effective range of 1,830 metres (1.14 mi) as an area suppression weapon. The first upgunned Stryker, known as the "Dragoon" for the 2nd Cavalry Regiment the vehicles will be part of, was delivered in October 2016,[22][23] and the first Infantry Carrier Vehicle - Dragoon (ICVD) was delivered to the 2CR in Germany in December 2017.[24]
The ATK MK44-ABM variant of the Bushmaster was selected in 2018 by the Spanish Army to equip the Tizona turret of the Line version (IFV) of the Dragón IFV, the replacement of the Pegaso BMR.[25]
Programming kit
[edit]A programming kit from Rheinmetall Oerlikon can be adapted to the Mk44 Bushmaster. With this kit, AHEAD 30mm air-burst ammunition can be shot from this cannon. The kit is the same as the ones used on the autocanons MK 30-2/ABM and the Oerlikon KCE, and was adapted for the Mk44.[26]
Users
[edit]30 mm cannons
[edit]- Army: AS21 Redback (EOS T-2000 turret)[27]
- Army: Patria AMV (Elbit UT30 Mk2 turret)
- Army: Sentinel II 8×8, Sentinel II 6×6 (with Elbit UT30 turret)[33]
- Army: Pindad Cobra IFV (ARES UT30 MK2 turret)[34]
- Navy: Mamuju-class, Pari-class patrol vessel, Pollux-class research vessel and Clurit-class fast attack craft
- Coast Guard: Tanjung Datu-class patrol vessel, Pulau Nipah-class patrol vessel and Bintang Laut-class patrol vessel
- Coast Guard: Hateruma-class patrol vessels, Kunigami-class patrol vessels (later ships), & Iwami-class patrol vessels
- Common tactical wheeled vehicle:
- Army: Freccia EVO (Combat and Reconnaissance variants) [36]
- Army: Mowag Piranha V[42]
- National Guard: LAV-700 IFV (CMCT turret)[43][44]
- Army: Piranha V - Dragon (219 VCR, 14 VCR-PC, 58 VEC) [45]
- Navy: Tachin-class frigate, Naresuan-class frigate, Krabi-class offshore patrol vessel, Leamsing-class patrol craft (gun), T.991-class coastal patrol craft, T.994-class coastal patrol craft, Angthong-class amphibious transport dock and Ladya-class mine countermeasure vessel
- Army: XM1296 Stryker Dragoon, KTO Rosomak (Hitfist-30P) [48]
- Army: XM1296 Stryker Dragoon
- USMC: ACV (Iveco SuperAV with Kongsberg MCT-30 turret)
- Navy: San Antonio-class transport ship, Littoral combat ship and Zumwalt-class destroyer
- Air Force: AC-130W, AC-130J (GAU-23/A)
- Coast Guard: Polar Security Cutter[49]
Munitions
[edit]
| name | short description | notes |
|---|---|---|
| MK238 | High Explosive Incendiary-Tracer (HEI-T) | This round self-destructs if it misses its target.[50] |
| MK239 | Target Practice Traced (TP-T) | training ammunition, ballistically matched with the MK264.[51] |
| MK258 | Armor Piercing, Fin Stabilized, Discarding Sabot-Tracer (APFSDS-T) | The round is designed to be "supercavitating" to increase its effectiveness when fired at targets like underwater mines.[52] |
| MK264 | Multi Purpose Low Drag-Tracer(MPLD-T) | Light armor-piercing capability with a delayed explosive reaction using a chemical fuze. It is available with and without Self Destruct (SD). |
| MK266 | High Explosive Incendiary-Tracer (HEI-T) | An update to an earlier round, with enhanced range.[53] |
| MK310 | Programmable Air Burst Munition-Tracer (PABM-T) | Can be programmed to explode in the air above target to wound or kill enemies behind cover.[54] |
| MK317 | Target Practice Discarding Sabot-Tracer (TPDS-T) | A training round.[55] |
| PGU14/B | Armor Piercing Incendiary (API) | A relatively lightweight projectile with a core of dense depleted uranium penetrator.[56] |
| PGU13D/B | High Explosive Incendiary (HEI) | Aircraft mounted cannons use the round against personnel, trucks, ammunition storage, and other targets.[57] |
| PGU15A/B | Target Practice (TP) | A training round with the same ballistic properties of PGU13D/B.[58] |
See also
[edit]- Bushmaster 25 mm chain gun
- Bushmaster III 35/50 mm chain gun
- Bushmaster IV 40 mm chain gun
- 30mm Shipunov 2A42—Soviet/Russian autocannon
- 30mm L21A1 RARDEN—British autocannon
- Future Combat Systems Infantry Carrier Vehicle
References
[edit]- Notes
- ^ "AIR FORCE CANCELS 30 MM CANNON PROGRAM FOR AC-130U GUNSHIPS - Inside the Air Force, 11 July 2008". Archived from the original on 28 September 2011.
- ^ "Scott, Richard, ASCG enhances Type 23 close-in defence, International Defence Review, 30 October 2007". Archived from the original on 4 July 2009. Retrieved 14 June 2009.
- ^ "30 mm SMASH Remote Controlled Stabilized Naval Gun System". Aselsan. Retrieved 7 December 2020.
- ^ Schanz, Marc V.; Sirak, Michael C. (October 2008). "Air Force World". Air & Space Forces Magazine. Vol. 91, no. 10. Archived from the original on 13 May 2025. Retrieved 19 January 2013.
- ^ GAU-23 30mm Automatic Cannon Receives Type Classification Archived 11 December 2012 at the Wayback Machine - Prnewswire.com, 9 July 2012
- ^ Mk-46 GWS Archived 2 November 2014 at the Wayback Machine - Seaforces.org
- ^ Navy Orders Six More General Dynamics Littoral Combat Ship MK46 Mod 2 Gun Weapon Systems Archived 2 November 2014 at the Wayback Machine - Guns.com, 21 March 2013
- ^ Navy Swaps Out Anti-Swarm Boat Guns on DDG-1000s Archived 31 October 2014 at the Wayback Machine - News.USNI.org, 5 August 2014
- ^ "Orbital ATK: Placing its Programmes on Target". Mönch Publishing Group. Archived from the original on 11 August 2018. Retrieved 11 August 2018.
- ^ "30mm & 20mm x 173mm Munition System". www.orbitalatk.com. Archived from the original on 2 July 2017. Retrieved 19 April 2018.
- ^ Navy LCS Gun Could Get Potent Airburst Rounds to Take Out Drones. Military.com. 16 January 2020.
- ^ ANALYSIS: Terrahawk Paladin: Ukraine's New Drone Destroyer Arriving Just in Time for Winter. Kyiv Post. 12 October 2023.
- ^ "Ukraine conflict: Western countries pledge more air-defence equipment". Janes Information Services. 13 October 2023. Archived from the original on 14 October 2023.
- ^ UK delivers Terrahawk Paladin air defense system to Ukraine. Army Recognition. 12 October 2023.
- ^ "Orbital ATK rolls out XM813 automatic cannon for US Army Strykers". Jane's 360. Archived from the original on 11 August 2018. Retrieved 11 August 2018.
- ^ "Malcolm Baldrige National Quality Award 2007 Award Recipient" (PDF). Archived from the original (PDF) on 19 July 2013. Retrieved 8 December 2013.
- ^ Bigger, badder Bushmaster cannon in the works - Armytimes.com, 8 November 2013
- ^ 30-mm weapon system on display - Army.mil, 16 September 2014
- ^ US Army: Strykers Need Bigger Gun to Fight Russia - Defensenews.com, 24 July 2015
- ^ Firepower Upgrade Planned for GDLS Strykers - Defensenews.com, 14 October 2015
- ^ US Army Seeks New Stryker Capability Beyond Bigger Gun Archived 20 December 2016 at the Wayback Machine - Militarytimes.com, 1 March 2016
- ^ Army UpGuns Stryker Infantry With 30mm Cannon to Counter Russia in Europe Archived 30 October 2016 at the Wayback Machine - Scout.com/Military, 5 October 2016
- ^ Army's New Up-Gunned Stryker Shoots Farther, Hits Harder Archived 5 November 2016 at the Wayback Machine - Military.com, 31 October 2016
- ^ 2CR Receives the First 30mm Stryker in Europe Archived 22 March 2018 at the Wayback Machine. Defense Visual Information Distribution Service. 8 December 2017.
- ^ "Navantia y Elbit montarán este julio la primera torre Tizona en San Fernando". 11 July 2019. Infodefensa.com 11 July 2019
- ^ "30MM AIR BURST MUNITION PROGRAMMING KIT" (PDF). Archived from the original (PDF) on 16 February 2025.
- ^ ESD (27 July 2023). "AS21 Redback Emerges Victorious in Australia's Land 400 Phase 3 IFV Contest". euro-sd.com. Retrieved 11 November 2023.
- ^ "Trade Registers". armstrade.sipri.org. Retrieved 6 June 2023.
- ^ "Blindado Guarani recebe torre dotada de canhão - Forças Terrestres - ForTe". forte.jor.br. 1 July 2011. Archived from the original on 26 April 2018. Retrieved 19 April 2018.
- ^ "Оръдия Bushmaster, ракети Javelin и още броня. С какво ще са въоръжени новите "Страйкър" за армията | Информационен център на Министерство на oтбраната". armymedia.bg (in Bulgarian). 13 January 2024. Retrieved 13 January 2024.
- ^ Defense Industry Daily staff. "Czech APCs to Carry RAFAELs RCWS-30". Defense Industry Daily. Retrieved 11 November 2023.
- ^ "BAE Systems takes aim at Czech Army requirement with CV90 | Jane's 360". Archived from the original on 14 June 2017.
- ^ "Ghana approves the purchase of 19 Israeli armored vehicles from Elbit Systems". Defense Here. 17 October 2020. Retrieved 11 November 2023.
- ^ "Indonesian army to receive Pandur II Cobra IFVs". www.armyrecognition.com. 16 April 2019. Retrieved 29 October 2019.
- ^ "Leonardo Offers HitFist Turret for Spain's Dragón AFV". MilitaryLeak. 8 November 2020. Retrieved 16 June 2023.
- ^ "I programmi di acquisizione ed ammodernamento dell'Esercito Italiano – Analisi Difesa" (in Italian). 6 November 2023. Retrieved 11 November 2023.
- ^ Tomkins, Richard (16 March 2017). "Lithuania orders Bushmaster guns from Orbital ATK". United Press International. Archived from the original on 17 March 2017. Retrieved 17 March 2017.
- ^ Foss, Christopher F (17 March 2017). "Lithuanian Boxers to be armed with 30 mm MK44 cannons". IHS Jane's 360. London. Archived from the original on 17 March 2017. Retrieved 17 March 2017.
- ^ "Poland". www.leonardo.com. Retrieved 6 June 2023.
- ^ "Rosomak APCs To Be Outfitted with the ZSSW-30 Turrets. Contract Imminent". defence24.com (in Polish). 1 July 2022. Retrieved 11 November 2023.
- ^ "700 CBWP infantry fighting vehicles for the Polish Army". meta-defense.fr. 21 August 2023. Retrieved 11 November 2023.
- ^ "Blindatele Piranha 5 vor fi produse complet la Uzina Mecanică București, inclusiv pentru export". HotNews (in Romanian). 15 March 2022.
- ^ "1312-General Dynamics Land Systems - Saudi Arabia | exitarms". exitarms.org. Retrieved 9 September 2023.
- ^ "Trade Registers". armstrade.sipri.org. Retrieved 9 September 2023.
- ^ Editorial, Defense Brief (19 December 2021). "Spain's 8x8 Dragon VCR combat vehicle program enters construction phase". Defense Brief. Retrieved 24 January 2023.
- ^ Everington, Keoni (30 May 2019). "Taiwan's army repulses simulated Chinese beach assault | Taiwan News | 2019-05-30 17:01:00". Taiwan News. Retrieved 11 January 2024.
- ^ "Military police to get CM-34 armored vehicles - Focus Taiwan". Focus Taiwan - CNA English News. 25 August 2020. Retrieved 11 November 2023.
- ^ "Rosomak APCs for Ukraine. USA Confirms the Numbers". defence24.com (in Polish). 22 September 2023. Retrieved 11 November 2023.
- ^ Ong, Peter (21 April 2022). "USGC's Polar Security Cutters to Receive Mark 38 Mod 4 Guns". Naval News. Retrieved 24 April 2022.
- ^
"30x173mm ammunition suite: MK264 MPLD-T - MK239 TP-T - MK238 HEI-T/SD - MK258 APFSDS-T - 30mm HEAB-T - MK317 TPDS-T" (PDF). General Dynamics. Retrieved 22 October 2020.
High Explosive Incendiary Tracer with Self Destruct, MK238: Low cost proven HEI-T with reliable M758 point detonating fuze with self destruct
- ^ "30x173MM ammunition suite for Mk44 cannon" (PDF). General Dynamics. Retrieved 22 October 2020.
- ^
"Mk 258 Armor Piercing, Fin Stabilized, Discarding Sabot-Tracer (APFSDS-T) Anti-Mine Projectile Hydroballistic Ammo 30mm Ammunition". Global Security. Retrieved 22 October 2020.
The lethality of the round gives a simple look, shoot, kill capability to the helicopter crew enabling them to maintain a rapid tempo of operations and maximizing the tactical effectiveness of every mission while minimizing exposure to hostile forces.
- ^
"ATK receives U.S. Navy ammo order". United Press International. Arlington, Virginia. 8 March 2013. Retrieved 22 October 2020.
ATK's MK266, a modification to the PGU-13 High Explosive Incendiary 30mm round, features a tracer and non-self-destruct, low-drag fuse for enhanced performance at extended ranges.
- ^
Gloude, Don (1 September 2011). "25 x 59mm LW25 Programmable Air Burst Munition" (PDF). 2011 NDIA Gun & Missile Systems Conference. Retrieved 22 October 2020.
Inductive programming that is common with ATK's 30mm PABM-T Mk310; reliable and simple to integrate.
- ^
Gourley, Scott R. (18 August 2013). "Army Refines 30mm Ammunition Efforts for GCV". Defense Media Network. Retrieved 22 October 2020.
Target Practice Discarding Sabot-Tracer (TPDS-T) Mk. 317 [a quantity of 2,000 rounds will be required to be submitted].
- ^
Pike, John (9 January 1999). "PGU-14/B API Armor Piercing Incendiary [DU] 30mm Ammunition". Federation of American Scientists. Retrieved 22 October 2020.
The PGU-14/B API Armor Piercing Incendiary round has a lightweight body which contains a sub-calibre high density penetrator of Depleted Uranium (DU).
- ^
"30mm x 173 GAU-8/A Ammunition: PGU-13/B HEI – PGU-14/B API – PGU-15/B TP". General Dynamics. Retrieved 22 October 2020.
High Explosive Incendiary (HEI): Provides fragmentation and incendiary effects for use against personnel, trucks, ammunition storage, and many other targets.
- ^
Pike, John (9 January 1999). "PGU-15/B TP Target Practice 30mm Ammunition". Federation of American Scientists. Retrieved 22 October 2020.
The PGU-15/B TP Target Practice projectile simulates the exterior ballistics and provides a ballistic match to the HEI round and is used for pilot training.
External links
[edit]Mk44 Bushmaster II
View on GrokipediaThe Mk44 Bushmaster II is a 30 mm chain gun manufactured by Northrop Grumman, derived from the 25 mm M242 Bushmaster and incorporating approximately 70% of its parts to enhance logistical commonality.[1] Designed as a versatile medium-caliber autocannon, it employs an external power-driven chain mechanism for reliable operation in diverse environments, firing 30×173 mm fixed ammunition at a cyclic rate of up to 250 rounds per minute.[1][2] Introduced into service around 2004, the Mk44 has been integrated into ground vehicles such as the US Army Stryker, naval platforms including the Littoral Combat Ship and San Antonio-class amphibious transport docks, and aircraft like the AC-130 gunship, providing suppressive fire and anti-armor capability.[1][3] Variants such as the Mk44S Bushmaster Stretch enable reconfiguration for 40 mm ammunition, extending lethality against personnel and light vehicles while maintaining dual-caliber flexibility for operators.[3] Its battle-proven design supports international adoption, with recent integrations on platforms like Australia's next-generation infantry fighting vehicle and Poland's Borsuk, underscoring its role in modern networked warfare.[3][4]
Development and History
Origins and Initial Development
The Mk44 Bushmaster II 30 mm chain gun originated as a private venture by Alliant Techsystems (ATK), now part of Northrop Grumman, in the late 1980s to provide enhanced firepower over the existing 25 mm M242 Bushmaster while maintaining high parts commonality.[5] This scaling-up retained approximately 70% identical components to the predecessor, facilitating logistical compatibility and reducing development costs through proven chain gun technology featuring external power drive and positive round control.[5][1] The design emphasized reliability for vehicle-mounted applications, addressing emerging requirements for medium-caliber autocannons capable of engaging armored threats beyond the 25 mm's limits. A prototype of the 30 mm Bushmaster II was completed in mid-1989, with initial firing tests demonstrating over 500 rounds by October of that year.[5] Demonstrations occurred internationally, including in Austria, and a U.S. Navy trial involving 2,000 rounds further validated the weapon's performance in October 1989.[5] These early evaluations confirmed the gun's external power mechanism, dual-feed capability, and sustained fire rates, building on the M242's established external chain drive system originally adapted from helicopter armament technologies.[1] Initial production and integration followed in the early 1990s, with the Norwegian Army selecting the Mk44 in 1994 for arming the Hägglunds Combat Vehicle 90 (CV9030N) infantry fighting vehicle, leading to the first completed vehicles in 1995.[5] ATK also supplied units for U.S. Marine Corps prototypes of the Advanced Amphibious Assault Vehicle (AAAV), marking early adoption in amphibious assault platforms.[5] These milestones established the Mk44's role in modernizing light armored forces, entering operational service in the mid-1990s.[6]Key Contracts and Milestones
The Mk44 Bushmaster II chain gun's development began with a prototype completed in mid-1989, which had fired over 500 rounds by October of that year during initial testing.[5] On November 1, 2004, the U.S. Air Force Special Operations Command awarded ATK (now part of Northrop Grumman) an $8.8 million contract for research, development, testing, and evaluation of modifications to the Mk44, enabling integration into the AC-130U Spooky gunship for enhanced firepower against ground targets.[7] In 2006, the UK Ministry of Defence contracted for 26 Mk44 units valued at £15 million over eight years, with deliveries commencing late that year for integration into Warrior infantry fighting vehicle upgrades. By July 2014, ATK secured contracts exceeding $220 million to supply medium-caliber cannons, including Mk44 variants, to undisclosed U.S. allies, supporting export demands for armored vehicle armaments.[8] In September 2017, Taiwan's Ministry of National Defense awarded Orbital ATK a contract for Mk44 Bushmaster II autocannons to equip the Clouded Leopard infantry fighting vehicles, with the order announced on September 29 for domestic production integration.[9] On December 16, 2020, Northrop Grumman received a U.S. Army contract to deliver 95 XM813 Bushmaster chain guns—a Mk44 derivative—for the Stryker Medium Caliber Weapon system, enhancing lethality against armored threats.[10][11] A $37.7 million firm-fixed-price contract followed in September 2020 for long-lead materials to manufacture these cannons, building toward full-rate production.[12] In May 2021, this expanded via a $106 million modification for additional armored vehicle cannon production.[12] In September 2025, Northrop Grumman initiated shipments of Mk44 Bushmaster II guns to Poland for the Borsuk next-generation infantry fighting vehicle program, fulfilling a contract to arm these platforms with 30mm chain gun capability.[13]Evolution into Modern Variants
The Mk44 Bushmaster II chain gun underwent significant modifications in the mid-2010s to address operational requirements for enhanced ammunition versatility and lethality against evolving threats, including armored vehicles and low-flying aircraft. A key development was the XM813 variant, derived from the Mk44S configuration and selected by the U.S. Army in response to a March 2015 operational needs statement for upgrading Stryker Dragoon infantry carrier vehicles with a turreted 30x173mm medium-caliber weapon system. This variant incorporates a dual-feed system with linkless ammunition handling, enabling rapid switching between high-explosive and armor-piercing rounds while maintaining the chain gun's external power-driven mechanism for sustained fire rates up to 200 rounds per minute. Live-fire demonstrations of the XM813, conducted by Orbital ATK (now part of Northrop Grumman) in June 2017 at Big Sandy Range, Arizona, validated its performance with both 30mm and 40mm configurations, showcasing improved recoil management and integration compatibility.[14][15][16] Parallel advancements led to the Mk44 Stretch (Mk44S), an extended-receiver evolution of the original Mk44 designed to accommodate longer 30x173mm cartridges, including the programmable air-burst munition Mk310 PABM-T for point-detonate, air-burst, and delay-fuze modes effective against personnel and light armor at ranges beyond 4 kilometers. This variant retains approximately 60% parts commonality with the 25mm M242 Bushmaster for logistical efficiency but introduces modular upgrades allowing field conversion to fire 40mm "Super Forty" ammunition, providing overmatch capability without full weapon replacement. Northrop Grumman integrated the Mk44S into platforms like the Polish Borsuk infantry fighting vehicle, with initial shipments beginning in 2025 to enhance firepower against modern threats.[3][17][18] The Mk44S further evolved for international programs, such as Australia's Land 400 Phase 3 acquisition of 129 units for the Hanwha Redback infantry fighting vehicle, announced in June 2024 with deliveries starting in 2026 to support interoperability with U.S.-developed advanced munitions suites. These variants emphasize dual-recoil systems and compact designs for remote weapon stations, reducing crew exposure while enabling precise engagement in urban and open terrain. Ongoing upgrades focus on software-defined fire control for smart munitions, ensuring the Bushmaster lineage adapts to counter-drone and peer-adversary scenarios without compromising the proven reliability of over 11,000 fielded chain guns.[19][20][21]Design and Technical Features
Core Mechanism and Components
The Mk44 Bushmaster II is a chain-driven autocannon that employs an external electric motor to power a continuous roller chain loop, which reciprocates the bolt assembly to load, fire, and extract rounds, ensuring consistent ammunition feed velocity and positive round control throughout the cycle.[22] This mechanism, derived from the M242 Bushmaster design, enables operation in single-shot, burst, or full-automatic modes at a cyclic rate of 200 rounds per minute, powered by 1.0 horsepower at 24 volts DC.[22] The open-bolt firing configuration positions the bolt rearward when idle, minimizing risks of premature ignition from residual heat or hangfires.[22] Central to the system is the receiver assembly, weighing 122 pounds (55.3 kg), which encases the chain drive sprockets, bolt carrier, and firing pin mechanism, facilitating the linear motion that chambers and extracts cartridges.[22] The feeder assembly, at 69 pounds (31.3 kg), incorporates delinking and rammer functions to strip 30×173 mm (or compatible 30×170 mm) linked ammunition from belts, select between dual feeds via clutches and sprockets, and advance rounds into the chamber with minimal disruption.[22] [23] The barrel assembly, the heaviest component at 153 pounds (69.4 kg), features a rifled bore optimized for high-velocity projectiles and quick-change capability for caliber adaptation, such as to 40 mm with minimal receiver modifications.[22] [23] Additional integrated elements include forward-ejecting case mechanisms to reduce crew exposure and anti-hangfire devices that interrupt the cycle if a round fails to fire promptly, enhancing operational safety under sustained fire conditions generating up to 8,000 pounds (35,586 N) of recoil.[22] The overall gun assembly totals 344 pounds (156 kg), with approximately 70% parts commonality to the 25 mm M242, promoting logistical simplicity and reliability in vehicle-mounted applications.[22]Integration Capabilities
The Mk44 Bushmaster II chain gun features a modular design that facilitates integration into diverse remote weapon stations, manned turrets, and direct-fire mounts across ground, naval, and aerial platforms, leveraging 70% parts commonality with the 25 mm M242 Bushmaster for reduced logistics and integration risks.[3][2] This architecture supports dual-feed ammunition handling, external power requirements of 28 VDC at up to 2 kW, and compatibility with fire-control systems via MIL-STD-1760 interfaces or custom adapters, enabling seamless incorporation into stabilized turrets without extensive vehicle modifications.[24] In ground vehicles, the Mk44 integrates into infantry fighting vehicles and armored personnel carriers via turrets such as the Kongsberg Protector Remote Weapon Station on the U.S. Army Stryker Dragoon, where the XM813 variant provides stabilized 30x173 mm firepower.[25] It has been selected for the U.S. Marine Corps Amphibious Combat Vehicle (ACV-30), with BAE Systems delivering full-rate production units armed via a remote turret as of May 2024.[26] Internationally, integrations include Poland's Borsuk IFV, with Northrop Grumman initiating deliveries of Mk44 units in September 2025 for HSW S.A. turrets; Australia's Redback IFV under Hanwha Defense, incorporating the Mk44 Stretch variant in June 2024 for enhanced lethality; and Spain's Dragón IFV with the ATK Mk44-ABM in the Tizona turret, contracted in 2018.[4][19][13] Naval applications emphasize mountings on surface combatants and support vessels, such as the Mk46 Mod 1 variant integrated into the U.S. Navy's Mk 38 Mod 4 weapons station, operable remotely from the combat information center or locally at the turret with stabilized elevation from -20° to +85°.[1] The system's lightweight barrel and recoil management allow retrofitting onto amphibious transport docks like the USS Green Bay (LPD-20 without compromising stability.[2] Aerial integration targets gunship and close air support roles, with the Mk44 adapted for podded or internal mounts on platforms like U.S. special operations AC-130 variants, providing sustained 200-300 rounds-per-minute rates in high-vibration environments through chain-driven reliability and quick-change barrels.[27][24] Overall, these capabilities stem from the gun's external power operation and minimal crew interface, prioritizing low-signature, high-availability deployment in networked kill chains.[3]Safety and Reliability Features
The Mk44 Bushmaster II chain gun employs an anti-hangfire safety mechanism designed to prevent delayed ignition of ammunition, ensuring operational security during handling and firing sequences.[22] It is available in an open bolt configuration, which maintains the bolt in a rearward position when not actively firing, thereby mitigating cook-off risks from residual barrel heat and eliminating a chambered round in the idle state.[22] Forward case ejection directs spent casings away from the turret interior and personnel, reducing potential hazards from hot brass impacting crew areas or equipment.[22] Reliability is enhanced through the chain gun's external power drive system, which employs a roller chain to cycle the bolt, minimizing internal mechanical stress and wear compared to recoil-operated designs.[2] The weapon demonstrates high mean rounds between failures exceeding 22,000, supporting sustained performance in demanding field conditions across NATO platforms.[28] A dual-feed system allows seamless switching between ammunition types without reconfiguration, contributing to operational flexibility while maintaining feed reliability via constant velocity mechanisms.[22] Design simplicity facilitates low-maintenance requirements, with 60% logistics commonality and 90% operator and maintenance training overlap with the M242 Bushmaster, reducing lifecycle costs and downtime.[22] These attributes, battle-proven in vehicle integrations, prioritize crew safety and system uptime through minimal intrusion into confined turret spaces and robust construction tolerant of environmental stressors.[2]Variants
XM813 Variant
The XM813 is a 30×173 mm chain gun variant of the Mk44 Bushmaster II, manufactured by Northrop Grumman as a derivative optimized for medium-caliber weapon systems on armored vehicles.[3] It maintains approximately 90% parts commonality with the Mk44 for logistical compatibility while incorporating enhancements such as a dual-feed mechanism enabling selective firing of 30 mm and 40 mm rounds from separate ammunition belts.[29] The design emphasizes compactness, with a weight of around 160 kg and dimensions facilitating integration into existing turrets without major modifications.[29] Developed to address U.S. Army requirements for improved firepower on infantry carrier vehicles, the XM813 features a selectable rate of fire up to 200 rounds per minute and compatibility with advanced munitions, including the MK310 programmable air-bursting round for point-detonate, air-burst, and delay fuzing modes.[30] Orbital ATK (now Northrop Grumman) demonstrated the XM813 in live-fire tests as early as June 2017, showcasing its integration into remote weapon stations for enhanced protection and lethality against armored threats.[15] The variant builds on the Mk44S configuration, retaining chain-driven operation and external power for reliability in sustained fire scenarios.[18] The U.S. Army selected the XM813 for the Stryker Dragoon's 30 mm Medium Caliber Weapon System, mounting it in a Kongsberg Protector remote turret to equip infantry carrier variants with direct-fire capability against light armor and personnel at ranges exceeding 3,000 meters.[25] In December 2020, Northrop Grumman secured a contract valued at up to $105 million to produce and deliver XM813 units for an additional brigade combat team, supporting fielding across multiple Stryker-equipped units.[31] This adoption underscores the XM813's role in modernizing legacy platforms with minimal redesign, leveraging proven Bushmaster reliability while enabling programmable ammunition for countering drones and dismounted threats.[11]Mk44 Stretch and Mk44S
The Mk44 Stretch, designated as the Mk44S, is an advanced variant of the Mk44 Bushmaster II 30 mm chain gun developed by Northrop Grumman, featuring dual-caliber compatibility for 30x173 mm ammunition with the capability to upgrade to 40 mm Super Forty rounds via field modifications.[3][17] This design extends the barrel length and incorporates enhancements for improved lethality, range, and ammunition versatility, maintaining the chain gun's external power drive, positive round control, and constant recoil system for sustained fire rates up to 200 rounds per minute in single-shot, burst, or fully automatic modes.[17] Key technical advancements in the Mk44S include simplified maintenance through modular components and high parts commonality with the baseline Mk44, enabling rapid reconfiguration between calibers without major disassembly, which supports logistics efficiency in operational environments.[17] It integrates with advanced fire control systems and munitions such as the 30 mm Mk310 Programmable Air Burst Munition-Target Practice (PABM-T), demonstrated in live-fire tests on light armored vehicles for engaging personnel, light armor, and aerial drones at extended ranges beyond 2,000 meters.[17] The system's recoil mitigation and dual-feed mechanism allow selective ammunition loading, enhancing tactical flexibility for ground combat vehicles and naval mounts.[3] Deployment of the Mk44S has focused on infantry fighting vehicles and maritime platforms, with Northrop Grumman announcing integration into Hanwha Defense Australia's Redback IFV program on June 4, 2024, to equip up to 129 vehicles under the Australian Army's LAND 400 Phase 3 contract, emphasizing overmatch against armored threats through compatibility with U.S. Army-developed smart munitions.[19] Naval applications include mounting on BAE Systems' Mk 38 Mod 4 remote weapon station, where it has been tested for engaging surface and air targets, leveraging the chain gun's reliability in maritime conditions with minimal degradation from saltwater exposure or vibration.[17] These integrations prioritize empirical performance metrics, such as muzzle velocity exceeding 1,000 m/s for 30 mm rounds, over unverified claims of superiority, with field data confirming low failure rates under prolonged firing sequences.[3]Other Specialized Configurations
The Mk44 Bushmaster II has been configured for naval applications, notably in the U.S. Navy's Mk 46 Mod 2 Gun Weapon System (GWS), which integrates the 30 mm chain gun into a stabilized mount for close-in defense against small surface threats like fast attack craft. Developed for littoral combat ships and other surface vessels, the Mk 46 system employs the Mk44's dual-feed capability to alternate between high-explosive and armor-piercing rounds, with a rate of fire up to 200 rounds per minute and effective range exceeding 2 km against surface targets. This configuration incorporates seawater-resistant components and remote operation to enhance survivability in maritime environments.[1][7] An airborne variant, designated GAU-23/A, adapts the Mk44 for fixed-wing gunships, arming the U.S. Air Force AC-130J Ghostrider and U.S. Marine Corps Harvest Hawk systems as a side-firing weapon for close air support and precision strikes on ground targets. Optimized for aerial integration, the GAU-23 retains the Mk44's chain-driven mechanism but features reinforced mounting for vibration and recoil management during sustained low-altitude firing, compatible with 30x173 mm ammunition including programmable air-burst rounds for suppressive fire against personnel and light vehicles. Initial integration occurred on AC-130U platforms around 2005, with upgrades for newer models emphasizing reliability in high-G maneuvers and night operations.[3][7][32] Additional specialized setups include dual-caliber demonstrations of the Mk44 in 30 mm and 40 mm configurations, allowing modular barrel swaps for enhanced lethality against drones or heavier armor without full system redesign, as shown in 2017 live-fire tests by Orbital ATK (now Northrop Grumman). These variants prioritize rapid reconfiguration for counter-unmanned aerial system (C-UAS) roles on remote weapon stations.[33]Ammunition and Munitions
Standard Compatible Rounds
The Mk44 Bushmaster II chain gun is chambered for the 30×173 mm cartridge family, enabling compatibility with a range of conventional, non-programmable ammunition types originally developed for systems like the GAU-8 Avenger.[34] These rounds provide versatile engagement options against armored vehicles, personnel, and materiel targets, with muzzle velocities typically exceeding 1,000 m/s depending on the projectile.[35] Key standard compatible rounds include the PGU-13D/B High-Explosive Incendiary with Tracer (HEI-T), which features a point-detonating fuze for fragmentation and incendiary effects against soft and lightly armored targets, achieving effective ranges up to 2,000 meters.[35] The MK264 Armor-Piercing Fin-Stabilized Discarding Sabot with Tracer (APFSDS-T) employs a tungsten penetrator for defeating medium armor at extended ranges, with ballistic performance matched to training variants for consistent fire control solutions.[34] Armor-Piercing Incendiary (API) rounds, such as those in the GAU-8 suite, incorporate incendiary fillers to ignite post-penetration effects on fuel or ammunition stores.[36] For training and qualification, the MK239 Target Practice with Tracer (TP-T) serves as a low-cost, ballistically similar inert round to the MK264, minimizing wear on the weapon while supporting accurate gunnery practice.[35] These munitions utilize linked belts for dual-feed systems, with the Mk44's design accommodating seamless switching between lethal and practice loads during operations.[3] All standard rounds maintain interoperability with NATO-standard 30 mm systems, ensuring logistical compatibility across allied platforms.[36]Advanced and Programmable Munitions
The Mk44 Bushmaster II chain gun is compatible with programmable airburst munitions (PABM) in 30x173mm caliber, enabling time- or distance-fuzed detonation for enhanced lethality against personnel, drones, and targets behind cover.[3] These rounds feature an inductive or coil-based fuze-setting system integrated into the weapon platform, which programs the fuze based on measured muzzle velocity without requiring operator intervention or internal round power sources.[37] The fuze arms only upon loading and supports modes such as point-detonation for direct impacts or airburst for overhead fragmentation, with effective ranges up to 2,000 meters against dismounted threats.[38] Northrop Grumman-developed PABM variants, including multi-purpose airburst tracer (MPAB-T) rounds, are optimized for the Mk44 and its derivatives like the Mk44S and XM813, providing rear-set fuzes for maximum explosive fill and compatibility with dual-feed mechanisms.[18] Rheinmetall's 30mm ABM programming kit, designed specifically for the Mk44, replaces the standard muzzle brake to deliver precise velocity data for fuze programming, supporting both single-shot and automatic fire at muzzle velocities around 1,100 m/s and projectile masses of 360 grams.[39] These munitions achieve fragmentation effects superior to unprogrammed high-explosive rounds, with demonstrations showing effective neutralization of simulated infantry and light structures.[15] General Dynamics Ordnance and Tactical Systems offers 30mm PABM compatible with the Mk44, featuring automatic fuze-setting and no degradation in rate of fire (up to 200 rounds per minute), which has been integrated into platforms like the Stryker Dragoon for countering obscured or aerial threats.[38] Live-fire tests by Orbital ATK (now Northrop Grumman) in 2017 validated PABM performance against combat-replicated targets, highlighting reduced collateral damage compared to unguided alternatives due to precise burst timing.[15] While primarily 30mm-focused, the Mk44's modular design allows limited 40mm PABM firing in stretch configurations, though this requires specific barrel adaptations.[18] Operational use, such as in Polish Rosomak vehicles during conflicts, confirms reliability of these munitions in automatic burst modes against dynamic targets.[40]Performance with Specific Ammo Types
The Mk44 Bushmaster II demonstrates varying ballistic performance depending on the 30x173mm ammunition type employed, with muzzle velocities ranging from approximately 980 m/s for armor-piercing incendiary (API) rounds to over 1,380 m/s for armor-piercing fin-stabilized discarding sabot-tracer (APFSDS-T) projectiles.[1] For APFSDS-T variants, such as the MK258, the gun achieves muzzle velocities up to 1,600 m/s, enabling penetration exceeding 100 mm of rolled homogeneous armor (RHA) at 1,000 m, with dispersion under 0.4 milliradians for precise engagement of lightly armored vehicles at ranges beyond 2,000 m.[34][41] These kinetic energy rounds leverage the chain gun's 200 rounds-per-minute cyclic rate to deliver sustained anti-armor fire, though higher velocities contribute to increased barrel wear compared to lower-velocity explosive rounds.[22] High-explosive incendiary-tracer (HEI-T) ammunition, fired at around 1,080 m/s, prioritizes fragmentation and incendiary effects against soft and lightly protected targets, with effective ranges up to 3,000 m in land applications.[1][42] The round's lower velocity relative to APFSDS-T results in reduced recoil impulse variation—typically 6,500 lb (28,913 N) across 30mm loads—but provides broader area lethality through blast and fire, suitable for suppressive fire or engaging infantry in cover.[16] Similarly, semi-armor-piercing high-explosive incendiary-tracer (SAPHEI-T) rounds maintain comparable velocities of 1,080 m/s, offering balanced penetration against thin armor (up to 25-30 mm RHA at close range) combined with post-penetration explosive effects.[1] Advanced programmable munitions like the MK310 programmable air-bursting munition-tracer (PABM-T) enhance versatility, programmed via the gun's fire control for airburst, point-detonating, or delay modes to defeat defilade targets such as personnel behind obstacles.[17][43] With muzzle velocities akin to HEI-T (approximately 1,000-1,080 m/s), these rounds extend effective engagement to 2,000+ m against fleeting or concealed threats, increasing hit probability by up to 3-5 times over unprogrammed equivalents in testing scenarios, though they require compatible dual-feed systems for on-the-fly switching.[35] Across ammo types, the Mk44's external power drive ensures consistent 100-200 rpm selectable rates, minimizing dispersion from recoil-induced platform motion.[22]Deployment and Users
Ground Vehicle Integrations
The Mk44 Bushmaster II chain gun has been integrated into multiple ground vehicle platforms, primarily infantry fighting vehicles (IFVs) and wheeled armored personnel carriers, to provide enhanced anti-armor and anti-personnel capabilities through its 30x173mm ammunition.[24] These integrations often occur via remote weapon stations or turrets, allowing for stabilized firing and compatibility with programmable munitions.[44] In the Polish KTO Rosomak wheeled IFV, the Mk44 Bushmaster II is mounted in the ZSSW-30 remote-controlled turret, enabling the vehicle to engage targets at ranges up to 4,000 meters with high-explosive and armor-piercing rounds.[45] Poland operates over 900 Rosomak variants, some of which have been donated to Ukraine for operational use, including firing airburst munitions in combat scenarios as of late 2024.[46] The system has demonstrated reliability in Polish Marine Corps testing, firing over 200 rounds per minute in burst modes.[45] The U.S. Army's Stryker Dragoon variant incorporates the XM813 Bushmaster II, a dual-feed configuration derived from the Mk44, mounted in a manned turret to upgrade the vehicle's firepower against lightly armored threats.[32] This integration, tested since 2017, allows selective feeding of high-explosive and armor-piercing ammunition, with over 300 Stryker vehicles retrofitted by 2020.[32] Poland's next-generation Borsuk IFV employs the Mk44 Stretch (Mk44S) variant in its ZSSW-30 turret, providing increased barrel length for improved muzzle velocity and range.[28] Deliveries of the guns to Poland began in September 2025, supporting the vehicle's development for enhanced mobility and protection in mechanized infantry roles.[4] Australia's Hanwha Redback IFV, selected under the LAND 400 Phase 3 program, integrates the Mk44S chain gun to equip 129 vehicles starting in the late 2020s, with the partnership announced on June 3, 2024.[19] This configuration emphasizes compatibility with advanced munitions for urban and open-terrain engagements.[47] The Czech Republic's CV90 IFVs feature the Mk44 Bushmaster II in a 30mm configuration, with turret elevation up to 70 degrees for overhead firing, as part of modernization efforts evaluated in procurement trials.[48]Naval and Other Platform Uses
The Mk44 Bushmaster II chain gun has been adapted for naval applications, primarily in remote weapon stations for engaging fast inshore attack craft and asymmetric surface threats. The United States Navy integrates the Mk44 into the Mk 46 Mod 2 Gun Weapon System, a remotely operated turret designed for close-in protection on surface combatants. This system equips the Zumwalt-class destroyers (DDG-1000), where each ship mounts two such turrets, each firing 30x173mm ammunition at rates up to 200 rounds per minute. Live-fire testing of these guns on USS Zumwalt occurred on May 20, 2020, demonstrating effectiveness against small boat swarms.[49] The Mk 46 also supports integration on amphibious ships like the San Antonio-class LPD-17, enhancing ship self-defense capabilities with its dual-feed mechanism allowing rapid ammunition switching.[1] The Royal Navy has selected the Mk44 for its 30mm gun systems to bolster defenses against fast attack craft, with integrations on platforms via partnerships like BAE Systems' Mk38 Mod 2/3 variants upgraded to include the Bushmaster. These systems feature reduced dispersion and low lifecycle costs compared to alternatives, enabling precise fire from stabilized mounts.[2] The Mk44 Stretch variant, an extended barrel configuration, has been tested on the MSI Mk38 Mod 4 station, further extending effective range for maritime patrol vessels and frigates.[3]
Beyond naval use, the Mk44 serves in aerial platforms through its GAU-23/A variant, a lightweight adaptation for gunships. The United States Air Force equips the AC-130J Ghostrider with the GAU-23/A, providing precision fire support with programmable airburst munitions against ground and maritime targets.[3] The U.S. Marine Corps integrates it into the Harvest Hawk kit for rapid aerial firepower deployment from transport aircraft. This configuration maintains the chain gun's reliability in high-vibration environments, with overmatch capability via advanced 30mm rounds.[3] No widespread adoption on rotary-wing aircraft has been reported, though the design supports potential helicopter integrations.[2]
International Adoption and Recent Contracts
The Mk44 Bushmaster II chain gun has seen adoption by multiple allied nations for integration into wheeled and tracked armored fighting vehicles, enhancing firepower against armored threats and low-flying aircraft. Lithuania selected the Mk44 in March 2017 to arm its Vilkas 8x8 infantry fighting vehicles, with Orbital ATK (now Northrop Grumman) contracted to supply and integrate 90 units via Rafael Advanced Defense Systems' Samson remote weapon stations, enabling compatibility with programmable air-bursting munitions.[50][51] Poland maintains the world's largest installed base of Mk44 systems, primarily on its Rosomak wheeled armored personnel carriers, where the gun provides dual-feed capability for 30mm and 40mm ammunition to engage diverse targets.[52] Taiwan acquired the Mk44 in 2017 for its indigenous CM-34 Clouded Leopard wheeled armored fighting vehicles, supporting the Republic of China Army's modernization efforts with a focus on medium-caliber firepower; subsequent U.S. approvals in June 2023 for $332.3 million in 30mm ammunition and spares further sustain this platform.[9][53] Australia awarded Northrop Grumman a contract in April 2024 to produce 129 Mk44 Stretch variants for its next-generation infantry fighting vehicles under the Land 400 Phase 3 program, with initial deliveries planned to commence integration testing.[19][54] Recent contracts underscore expanding demand amid regional security concerns. In September 2025, Northrop Grumman initiated deliveries of Mk44 Bushmaster guns to Poland's Huta Stalowa Wola for the Borsuk next-generation tracked infantry fighting vehicle, bolstering NATO interoperability and providing sustained access to U.S. supply chains for ammunition and parts.[13][55] Latvia's April 2025 selection of Elbit Systems' UT30 MK2 turrets for its armored vehicles is expected to incorporate the Mk44, aligning with broader Baltic procurement trends for standardized NATO-compatible systems.[56] These agreements reflect preferences for the Mk44's reliability, parts commonality with the U.S. M242 Bushmaster, and adaptability to remote turrets over European alternatives in cost-benefit analyses.[21]Operational Performance and Effectiveness
Testing and Live-Fire Demonstrations
In June 2017, Orbital ATK (now part of Northrop Grumman) conducted a live-fire demonstration of the Mk44 Bushmaster chain gun at Big Sandy Range in Arizona, firing both 30mm and 40mm ammunition, including programmable air burst munitions, against adobe structures, concrete blocks, steel panels, and simulated combat-defilade positions.[15] The weapon was integrated onto a Kongsberg Protector remote turret and a General Dynamics Land Systems light armored vehicle to evaluate its effects in potential upgrades for the U.S. Army's Stryker fleet using the XM813 variant, with observed outcomes including significant structural disruption to targets.[15][57] U.S. Army evaluations in March 2020 featured live-fire tests of the Mk44 Bushmaster II integrated on M1296 dragoon, M1128 mobile gun system, and M1126 Stryker infantry carrier variants during Training Support Activity Europe exercises, demonstrating sustained firing capabilities in dynamic scenarios.[58] Similarly, in March 2020, a Light Armored Vehicle (LAV) equipped with the Mk44S variant fired 30x173mm Mk 310 programmable air burst munitions, highlighting airburst effects against representative threats.[59] In June 2022, prior to the Eurosatory exhibition in Paris, Milrem Robotics performed the first live-fire test of its Type-X unmanned ground vehicle fitted with the Mk44 Bushmaster II via a Kongsberg Protector RT40 remote weapon station, achieving precision engagements with 30/40mm rounds from 2x75 ready ammunition stores.[60] Earlier developmental testing at Aberdeen Test Center in 2000 evaluated the Mk44 with MK 258 hydroballistic ammunition, firing 70 rounds in 5-round bursts into water, achieving velocities up to 1,410 m/s at entry, underwater travel with dispersion of 0.70–1.4 milliradians, and confirmed lethal effects against surrogate underwater targets at 25-meter depths and 75-foot slant ranges.[61] These demonstrations collectively validated the system's reliability, dual-feed mechanism, and adaptability across platforms, with no major mechanical failures reported in the cited events.[62][21]Combat-Relevant Applications and Data
The Mk44 Bushmaster II chain gun has been operationally employed in combat primarily via its GAU-23/A variant, integrated on U.S. Air Force AC-130J Ghostrider and AC-130W Stinger II gunships for close air support, air interdiction, and armed reconnaissance missions. These aircraft completed their initial combat sorties in Afghanistan beginning in June 2019, utilizing the 30mm cannon to engage ground targets with high-precision fire.[63][3] In aerial applications, the GAU-23/A delivers a cyclic rate of 200 rounds per minute with a recoil force of 8,000 pounds, enabling sustained suppression and destruction of lightly armored vehicles, personnel, and structures within an effective range of up to 3,000 meters on land targets. Programmable airburst munitions compatible with the system enhance lethality against dismounted infantry in defilade, while armor-piercing rounds target technical vehicles and light fortifications, as demonstrated in operational feedback from counter-insurgency environments.[64][4][22] Ground-based integrations, such as on the U.S. Army's M1296 Stryker Dragoon infantry carrier vehicle, have undergone extensive live-fire testing simulating combat scenarios, including engagements against simulated enemy positions and armored threats. A 2017 demonstration by Orbital ATK (now Northrop Grumman) involved firing 30mm and 40mm rounds at adobe walls, concrete blocks, and steel panels, confirming penetration and destructive effects representative of urban and asymmetric warfare targets. Reliability metrics from field exercises highlight over 1,600 global installations with battle-proven uptime, though detailed casualty or target neutralization data from ground combat remains classified or sparse due to the system's recent fielding post-2018.[15][22]Comparative Advantages Over Rival Systems
The Mk44 Bushmaster II's chain-driven mechanism confers inherent reliability advantages over gas-operated rivals like the Russian 2A42 autocannon, as the external power source enables consistent cycling and positive ammunition control without dependence on propellant gases or recoil forces, which can lead to failures in adverse conditions or with varied ammunition loads. This design yields mean rounds between failures exceeding typical gas-operated systems, with documented low life-cycle costs and minimal maintenance requirements in field use.[65] In comparison to dual-barrel systems such as the Rheinmetall Mk30-2, the Mk44 employs a simpler single-barrel configuration that reduces mechanical complexity, weight (approximately 156 kg for the gun assembly), and potential points of failure while maintaining comparable muzzle velocities around 1,080 m/s for standard 30x173mm rounds. The Mk44's selectable firing rates—single shot, burst, or 200 rounds per minute sustained—offer precise controllability superior to the Mk30-2's higher but less flexible dual-feed rates, which demand more intricate synchronization and increase vulnerability to jams under sustained fire.[66]| Feature | Mk44 Bushmaster II | 2A42 (Gas-Operated) | Mk30-2 (Dual-Barrel) |
|---|---|---|---|
| Operating Principle | Chain-driven, external power | Gas-operated | Gas-operated, dual barrel |
| Rate of Fire (sustained) | 200 rpm selectable | 200-550 rpm variable | ~200 rpm per barrel |
| Feed System | Dual-feed, rapid switch | Dual-feed | Dual-feed with ABM fuze |
| Reliability Focus | Positive round control | Prone to gas variability | Complex synchronization |