The United States Army continues to use the M2 .50 caliber machine gun, notably as a vehicle-mounted weapon. It is likely to remain in service for decades to come, but the Army announced this month that it will test an even larger caliber weapon, the Northrop Grumman XM913 50mm Bushmaster Chain Gun.
The US Army ordered 16 of the weapons for use during the XM30 Mechanized Infantry Combat Vehicle competition, which seeks to find a replacement for the legacy M2 Bradley Infantry Fighting Vehicle (IFV).
“The 50mm cannon is a critical component to the ICV’s future and is instrumental in helping the U.S. Army regain the lethality the Armor Brigade Combat Teams need to win the next fight and every fight after that,” explained John McCollum, director of business development at the guns operating unit for Northrop Grumman.
Chain Gun
The XM913 is the latest in a line of so-called “chain guns,” which emerged in the 19th century with unique weapons such as the Treeby Chain Gun. Patented by Thomas Treeby, it used a chain of chambers that could be fired in quick succession. The British Army tested it but ultimately rejected it due to its low-power caliber rounds and its complexity, which was prone to jamming.
Another attempt, the Guycot, failed as it employed fragile ordnance consisting of “rocket balls.”
Modern chain guns incorporate some concepts from the early hand-cranked Gatling gun, notably multiple barrels and manual loading and ejection of rounds, unlike traditional machine guns, which use the energy from a chemical reaction to chamber the next round.
The difference is that instead of manually hand-cranking the mechanism, an external power source cycles the weapon action via a continuous loop of chain. Even chain guns that employ just a single barrel are still electronically powered.
The Hughes Helicopter company developed the first chain gun in the early 1970s and patented the design. It has been used on a variety of systems in different calibers.
A significant advantage of chain guns is that a misfired round will not stop the functioning of the weapon, unlike with machine guns or other recoil-based weapons. This makes a chain gun inherently reliable. The other advantage is a much higher rate of fire.
The XM913 Specifications and Development
The XM913 is a larger, modernized version of the 35mm Bushmaster III chain gun, which evolved from the M242 25mm Bushmaster cannon. Development of the XM913 was undertaken at the Picatinny Arsenal in New Jersey, the headquarters of the U.S. Army Combat Capabilities Development Command Armaments Center.
The medium-caliber chain gun is chambered for 50x228mm (1.97 in.) caliber and was designed with a relatively slow rate of fire of either 100 or 200 rounds per minute. The largest chain gun produced by Northrop Grumman allows for rapid switching of the ordnance being fired.
“The XM913 will solidify battlefield advantage with its ability to fire 50x228mm advanced ammunition,” explained the Northrop Grumman website. “With dual feed, first round select capabilities, the XM913 ensures soldiers have the most effective ammunition to engage battlefield threats. The advanced ammunition suite includes High Explosive Air Bursting (HEAB) and Armor Piercing Fin Stabilized Discarding Sabot (APFSDS).”
Deliveries of the XM913 have already begun to the Combat Capabilities Development Command for equipping the XM30 prototypes produced by American Rheinmetall Vehicles and General Dynamics Land Systems (GDLS).
The XM30 Program
The XM30 program, previously known as the Optionally Manned Fighting Vehicle (OMFV), is the latest U.S. Army attempt to field a replacement for the Cold War-era M2 Bradley IFV.
In June 2023, the Army selected American Rheinmetall Vehicles and GDLS to build the XM30 prototypes. A winner could be selected in 2027.
According to current plans, the XM30 would carry less ordnance than the Bradley, but that would be offset by the fact that the 50mm chain gun would require fewer shots to destroy a target.
“This efficiency is especially important as future units operate more spread out and resupply becomes more difficult in contested environments,” Interesting Engineering explained.
It will still be necessary to make every shot count!
