The manufacturer claims that this reduces the heating and carbon fouling of the internals, simplifies field maintenance, and improves reliability.

[6] It was an approved personal purchase duty carbine of the United States Drug Enforcement Administration[7] in a special configuration called the M6A2 D-DEA, however, it is not standard issue.

The 5.56×45mm NATO UCIW weighs 6.25 lb (2.83 kg) and is apparently intended for use by UKSF dog handlers, team leaders, signallers and for use in vehicles and whilst conducting covert reconnaissance and close protection, replacing the 9×19mm Parabellum MP5K machine pistol in the latter role.

This rifle uses a midlength short stroke gas piston system to reduce recoil and increases the speed of follow up shots.

[13] It features an adjustable gas system to allow the user to adapt the rifle to different conditions and is designed to accommodate optics such as scopes and reflex sights.

It was developed for the United States Marine Corps' Infantry Automatic Rifle program, which sought to replace some M249s with a more maneuverable weapon.

Firing from an open bolt increases cooling and eliminates the potential for accidental discharges due to rounds "cooking off" in an overheated chamber.

This is due to the fact that when the trigger is pulled, the bolt slams forward under spring tension, stripping a round from the feeding device, chambering it, then firing it.

This sequence of events shakes the firearm and takes longer than a closed bolt design to fire the first round (greater lock time).

Magpul created a larger variation of their PMAG magazine, called the "Black Widow," with a blood-red follower for the 6.8mm round.

Weapons of this series come standard with Magpul MOE pistol grips, LWRCI proprietary compact stocks, and iron sights.