Special U.S. Military units use specialized weapons but you have to make a case that the U.S. needs to scrap it's basic infantry weapon before you get all upity about upgrading it. It's interesting to note that the U.S. scrapped the venerable old .45 automatic for an anemic (foreign made) 9mm while federal police agencies upgraded the .45.for basic service. My theory is that the strange determination of (mostly) democrats to put women in harms way in combat revealed that the tiny female hand couldn't deal with the substantial recoil of the .45.