There are many opponents of the Second Amendment, including more than a few politicians, who would like to see a ban on .50 caliber rifles. The Giffords Law Center described such firearms as ...

Deceptively light for its class at 26 pounds, the Tac-50 is a .50 caliber rotating bolt-action rifle boasting a 29-inch, high-quality Lilja barrel and McMillan’s signature fiber-glass stock.

Among the top weapons acquired by Mexican cartels and their U.S.-based straw buyers are the M249S belt-fed rifle and the Barrett .50 caliber rifle.

The desire to reduce the .50 caliber ammo's weight is part of the Corps' continuing effort to lighten its infantry and increase speed on the battlefield.