U.S. Army soldiers might soon enter battle wearing a robotic "third arm" that allows them to shoot a lot more accurately with their Colt M4 carbines.

The U.S. Army Research Laboratory (ARL) in Maryland is looking into the feasibility of developing a battery-powered weapons mount, which is being referred to as a "third arm." The main use of this third arm will be to provide a steadier platform that increases the accuracy of a soldier while firing his M4.

ARL also plans to examine the third arm's use in various fighting techniques, like shoot-on-the-move; close-quarters combat and shooting around corners with augmented reality displays.

The M4 is the only weapon currently being tested with the body-worn weapons mount. There are, however, plans to use other weapons such as the M249 squad automatic weapon and the heavier M240B machine gun with the third arm.

The third arm is also being designed to carry combat loads lugged by soldiers and free their hands for other tasks. Some soldiers are weighed down by combat loads weighing over 50 kg.

A prototype being tested by ARL is made of composite materials; weighs less than 1.8 kg and is attached to a soldier's protective vest.

"Right now we're just doing proof of concept, so we're not diving into the dirt with our only prototype," said Dan Baechle, a mechanical engineer at ARL.

"But that's something we would want to make sure we can do, because soldiers will be doing that."

ARL is conducting a pilot program in which a few soldiers use a third arm with an M4 carbine while firing their weapons at the Aberdeen Proving Ground in Maryland. These soldiers wear electromyography sensors on their arms and upper body to measure muscle activity to determine if they become more fatigued when shooting with the third arm.

"We're looking at a new way for the soldier to interface with the weapon," said Zac Wingard, a mechanical engineer at ARL's Weapons and Materials Research Directorate.

"It is not a product; it is simply a way to study how far we can push the ballistic performance of future weapons without increasing soldier burden."