This is all being driven by the perceived need for small arms that can defeat individual body armor. Which from where I sit signals a change for the better because Big Army usually is fixated on re-fighting the last war. This shows they're thinking ahead. The Abrams tanks and Apache helicopters are horribly ill-suited to MOUT and guerrilla warfare, but that's what we're stuck with because they were figuring the next war would be an armor battle against the USSR for Western Europe. S'Why the Corps is still fighting with Cobras (only re-christened "Viper"). Because for the way they fight, a 1500-rpm 20mm cannon beats a 625-rpm 30mm. And it still shoots the same anti-tank missile as the Apache.
Anyway, the 5.56 projectile has been deemed too light to adequately support their anti-IBA requirements. Yeah, they could go heavier still with projectile weight, but only at the cost of muzzle velocity (= less kinetic energy) and they'd have to use a tighter still twist than the M-4's already extremely tight 1:7 twist.
As the hot rodders say, there is no replacement for displacement.
Army Starts Testing Next Generation Squad Weapons In 27-Month Test
The U.S. Army is getting much closer to deploying the next generation weapon that could soon replace the M4 carbine and M249 light machine gun sometime in the early 2020s.
On Aug. 29, the Army announced it selected three defense companies to deliver prototype weapons for the Next Generation Squad Weapons (NGSW) program.
The new weapons must be lighter and able to penetrate the world's most advanced body armor from at least 600 meters away, defense insiders say.
"This is a weapon that could defeat any body armor, any planned body armor that we know of in the future," former Army Chief of Staff Gen. Mark Milley has said.
"This is a weapon that can go out at ranges that are unknown today. There is a target acquisition system built into this thing that is unlike anything that exists today. This is a very sophisticated weapon."
Follow the link in the headline for further details and pitchers.