U.S. Army Now Armed with Powerful XM913 50mm Cannon. In this video, we will explore the features and capabilities of the XM913 cannon and analyze how it may shape the future of warfare for the United States. Stay tuned!!! Picatinny Arsenal has developed an experimental American chain gun called the XM913, which is a more advanced and larger version of the 25 mm Bushmaster cannon. The XM913’s 50 x 228 mm shells are twice the diameter of the M242 Bushmaster’s 25×137mm shells, yet the cannon’s length is not significantly longer than the smaller weapon. Specifically, the XM913 is 117.7 inches in overall length, with 40.1 inches of the gun intruding into the turret, whereas the 25mm cannon is 105.2 inches in overall length, with 30.0 inches of the gun intruding into the turret.