Body armor.
Big Army is re-tooling in anticipation of an era when everybody on the battlefield will be wearing body armor. The poodle-shooter 5.56's projectiles are too low in mass to meet the requirements for defeating body armor. Which is precisely why Sig felt the need to think outside the box and redefine what "high pressure" is.
This round from a 16" barrel produces near as makes no difference identical muzzle energy to a 175-grain 7.62x51 NATO round from a 24" barrel.
And with armor-piercing projectiles, it will defeat all known body armors as well as any known to be in development.
Which was why I posted my #36 :(
“Which is precisely why Sig felt the need to think outside the box and redefine what “high pressure” is.”
U.S. Army spec’d.