For a Colonial Marine squad to survive engagement, it needs more than just rifles. Machine guns offer the Marines more firepower for offensive and defensive operations. The USCM picked the M56A2 Smart Gun as their machine gun of choice.
The M56A2 SMART GUN is a 10mm general-purpose automatic squad support weapon, effective out to 1500 meters. The pulse-action system employs a free-floating recoil-dampened rotating breech mechanism chambered for the M250 series 10mm x 28 caseless round. the gun also incorporates a muzzle booster to ensure the necessary operating forces from the large round. Cyclic rate is around 1200 rounds per minute.
The gun is constructed largely from molded carbon-fiber and light alloy stampings, though some interior parts of the mechanism are made from plastic. The replaceable barrel system is air-cooled, though a heat-sink attachment can be jacketed onto it. The system is mounted on an operator's harness and slaved to an infrared tracking system. As the name implies, the gun has 'smart' capabilities. Specifically, the M56A2 can aim itself. Using a targets infrared signature, it will 'steer' itself to aim at the target. While the marine operating the gun still has control of where to aim, it's best to let the M56A2 do it's job. The gun will not fire by itself. It still requires the operator to pull the trigger.
The entire gun assembly masses 17.82 kg. The length of the gun itself is 122 cm, and the length of the barrel is 54.5 cm.
The stabilized articulation arm is attached to the left hip mounting and plugged in via coaxial cable to the processor and power outlets in the breastplate. The gun itself is clipped and secured on the end of an free moving 'steady-cam' type harness with an articulating arm. This gives the gun a wide range of motion and targeting area. The actual weight of the gun is supported by the operator's shoulders and legs, allowing it to be used for extended periods of time with less fatigue.
The operator plugs this HMS (head mounted sight) into the tracking and comms system in the armor. the gun tracker is jacked into the process by a universal connector, and the gun itself must be powered up before the weapon is loaded. Power for the entire gun system is supplied by standard DV9 Lithium battery units, good for up to 50,000 rounds when fully charged. Both ends of the DV9 unit are plugged into the power leads that run from the articulation arm to the gun; common practice in the field is to let the battery hand free beneath the gun, where it is easily accessed in an emergency.
The M250 10mm x 28 ammunition is a 230 grain caseless projectile encased in a rectangular block of Nitramine. Higher powered that the M309 round for the pulse rifle, the M250 also significantly differs in having a selectable fuse setting. A switch on the hand grip is used to select the ammunition fusing, which is set electronically as the round is loaded into the chamber. The 'Super' setting is optimized against soft targets and will detonate the round on impact, while the 'Delay' setting explodes the shell only after penetrating the target armor.
The M250 ammunition is stored on a roll of continuous plastic non-disintegrating link belt in the ammunition drum, which can be reloaded in the field. The gun motor drives the feed mechanism as well as the rotating breech, and automatically loads each round off the belt and into the breech. In the event of a jam, the manual cocking handle at the side can be pulled to eject the round and clear the breech. This procedure can also be used to manually charge the mechanism. This will keep jams to a minimum.