Army researchers shrink the M-4 to half its size and weight

The Drive:

US. Army researchers are working to develop a personal defense weapon that offers the same muzzle velocity as a standard M4 carbinein a package that's half as long, half the weight, and uses smaller, lighter ammunition. The service's engineers say that the design features they are working with to achieve these results are readily scalable and could offer a path to lighter weight rifles and machine guns in the future, too.


In March 2019, the Army Research Laboratory (ARL), situated at Aberdeen Proving Ground in Maryland, test-fired an experimental design with a 10 inch-long barrel using ammunition with just a single gram of gunpowder, according to a story from TechLink. The gun demonstrated a muzzle velocity of more than 2,900 feet per second. An M4 firing standard 5.56x45mm M855A1 ammunition, which has around one and a half times as much powder, has an average muzzle velocity of around 2,970 feet per second.

“The goal is to get rifle-like velocities out of a very small weapon that is high capacity, that’s either adaptable for room-clearing or confined spaces,” said Zac Wingard, a mechanical engineer at ARL told TechLink....
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There is more on the construction and mechanics of the proposed weapon.  It would certainly be a benefit to troops in a confined environment.  A smaller weapon would also result in less fatigue for the troops on patrol.