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.
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-classlittoral 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 proximityairburst 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
The XM813 Bushmaster is based on the Mk44 and is offered as an upgrade for U.S. ArmyM1126 Stryker 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]
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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.