M1128 Mobile Gun System

Following the end of the Cold War some theorists believed that the existing suite of U.S. armored vehicles, designed largely to fight Soviet mechanized forces in Europe, were not well suited to the lower-intensity missions U.S. armed forces would be tasked with. This led to the development of a new armored fighting vehicle designed for lower-intensity combat, rather than large-scale battle.

By 1992, the Armored Gun System emerged as the top priority procurement program for the Army.[6] The Army requested proposals for a 20-ton air-droppable light tank to replace the M551 Sheridan. The Army sought 300 AGS systems to go to the 82nd Airborne Division and the 2nd Armored Cavalry Regiment. Four competitive bids emerged,[7] and in June 1992, the Army selected the FMC Close Combat Vehicle, Light proposal.[8] This was later type-classified as the M8 Armored Gun System. In 1996, the Pentagon canceled the AGS due to budget cuts across the services.

The Interim Armored Vehicle program included a requirement for a Mobile Gun System. A team of GM Defense of Canada and General Dynamics Land Systems proposed an MGS variant of the LAV III. United Defense LP proposed an M8 Armored Gun System (AGS) and two variants of the Mobile Tactical Vehicle Light (MTVL); one with the AGS turret and 105mm gun, and another with a 90mm gun.[9] Two other competing contractors submitted bids for infantry carriers, but declined to submit offers for the MGS requirement.[10]

Unlike the infantry carrier variants, MGS prototypes were not evaluated on the Army's proving grounds. This resulted in protests from lawmakers and industry officials. The service maintained that vehicle trials would be unnecessary and complicate the competition.[11]

GM-GDLS won the contract for both the infantry carrier and MGS, which was later type classified as the M1128.[12] GM-GDLS suspended work on the IAV while the Government Accounting Office evaluated UDLP's protest of the award. This protest was denied in April 2001.[13]

Soon after the contract was awarded, the MGS IOC date slipped two years from December 2001 to November 2003. The Army allowed GM-GDLS to substitute the Stryker ATGM variant for the MGS in the interim. In its protest, UDLP alleged that the Army had in fact known about the schedule slippage before awarding the contract, and unfairly disregarded this in their decision making.[14]

In 2000, the Army found its existing ammunition stockpile of 105mm rounds to be in poor condition, with more than half determined to be either unusable or obsolete. The Army solicited industry to produce new ammunition to replenish the stockpile.[9]

In March 2004, the Army approved the transfer of four AGS production vehicles to the 82nd Airborne Division to be used in Iraq. However, in June 2004, this plan was put on hold while the Army determined whether the MGS could meet the 82nd's requirements.[15] In August, the Army conducted an air-drop test of a Stryker M1132 Engineer Squad Vehicle weighted to simulate the load of the MGS. Around the same time, the Army identified issues with the air-dropability of the MGS, among the heavier of the Stryker family. Still more pervasive problems persisted with the autoloader.[16] In January 2005, the Army said it had ruled out fielding the AGS, saying the system lacked a spare parts inventory that would be required to maintain the vehicle for any significant length of time. The Army doubled down on its belief in the MGS, which it said it could begin fielding in summer 2006.[17]

After a Defense Acquisition Board review, the Pentagon, in October 2004, approved limited low-rate production of the MGS. During limited production, 14 vehicles would be produced. During this time, General Dynamics redesigned the ammunition handling system to be more reliable. In November 2004, the Pentagon approved an Army request to move the vehicle into low-rate production, to total 72 vehicle.[18]

After a Defense Acquisition Review, the Pentagon approved full-rate production of the MGS in February 2008.[19] However, the Army chose to defer production of new vehicles while it waited to validate fixes made to the MGS.[20]

Full-rate production was indefinitely deferred as of 2012.[21]

In late 2013, the U.S. Army began seeking to reintroduce an airdroppable mobile airborne protected firepower platform to provide fire support for air assault forces, a capability that had been absent since the retirement of the M551 Sheridan in 1997. General Dynamics initially considered modifying the wheeled Stryker MGS to meet the Mobile Protected Firepower (MPF) program requirement,[22][23] but the company instead entered a variant of the Griffin light tank.[24]

In May 2021, the Army announced they would divest all Mobile Gun Systems by the end of 2022. The decision was made following an analysis that found its autoloader had become expensive to maintain and that the M1128 had not been upgraded with a Double V-Hull, and that it was more efficient to eliminate the platform and focus on firepower improvements such as equipping Strykers with 30 mm cannons and CROWS-J mounts, providing better distributed lethality capabilities that will not be lost from removing the MGS.[5][25]

Canada had liquidated about half of its fleet of Leopard 1 Main Battle Tanks in the early 2000s, with the intention of replacing them with the Mobile Gun System, but the decision was reversed.[26]

Mobile Gun System firing

The MGS's low profile turret has a small silhouette, is stabilized and mounts a 105mm M68A1E4 rifled cannon with a fume extractor and an autoloader. The vehicle is primarily outfitted to support infantry combat operations; while it could take on some of the roles of a tank, it is not designed to engage in combat with tanks. The MGS can store 18 rounds of main gun ammunition, 8 in the autoloader's carousel and an additional 10 in a replenisher located at the rear of the vehicle.[27] It has a rate of fire of ten rounds per minute.[28]

The reduced height required of the Stryker to meet the C-130 transportability requirement proved particularly challenging when applied to the MGS. The reduced distance between the muzzle brake and the hull caused blast overpressures to develop. A solution was found where the "pepper pot" could be covered by a sheet of metal.[29]

The MGS's 105 mm cannon can fire four types of ammunition: the M900 kinetic energy penetrator to destroy armored vehicles; the M456A2 high explosive anti-tank round to destroy thin-skinned vehicles and provide anti-personnel fragmentation; the M393A3 high explosive plastic round to destroy bunkers, machine gun and sniper positions, and create openings in walls for infantry to access; and M1040 canister shot for use against dismounted infantry in the open.[30][31]

Because the vehicle was originally designed without air conditioning (A/C), crews were given cooling vests that circulate cooled water from outside the vehicle to the garment. Vehicle computers still overheated regularly. All MGS Stryker platforms have since been upgraded with A/C units.[32] The large weapon station and relatively smaller hatch can make emergency exits difficult.[1] Because the main cannon is separated from the crew compartment a gun stoppage during combat can only be cleared by disembarking from the vehicle.

The U.S. Army allocated nine Mobile Gun Systems to a battalion.[1] There were 27 Mobile Gun Systems per "Stryker brigade" in 2013, but later the Army cut the number per brigade to 10.[22] The Army bought 142 Mobile Gun Systems in total;[33] 3 were lost in combat. A three-vehicle MGS platoon operates organic to a Stryker infantry company, with one MGS in support of a Stryker infantry platoon.[34]

As of May 2017, a Stryker brigade combat team is equipped with three platoons of MGS Strykers and three platoons of ATGM Strykers in its weapons troop.[35]