According to the solicitation, the Dept. of Agriculture wants the guns to have an "ambidextrous safety, semiautomatic or 2 round [bursts] trigger group, Tritium night sights front and rear, rails for attachment of flashlight (front under fore group) and scope (top rear), stock collapsible or folding," and a "30 rd. capacity" magazine.
I wonder if it has anything to do with the fact that the military is sworn to protect and defend the US Constitution, while un-elected beaurocrats in the USDA don't have that safeguard.
In short, they know they can't get the military to start firing on civilians, so they're going to get someone else to do so.