Unless things have changed a lot since some friends were there, you take what the Army damned well gives you and if you get caught with a personal weapon you will be court-martialed, reduced in rank, fined and maybe jailed. And if you are caught using hollow point or expanding bullets you will be in double trouble. Freedom of choice in the Army is to do it their way. Maybe the Marines or some other service will haul around tons of personal weapons for you, in violation of all kinds of laws, and supply ammo to boot, but the Army definitely frowns on that sort of thing.
(I find reading here that the guys who claim they would take this or that have not been in the service, and have never been subject to any form of military discipline. The military doesn't like wiseguys who go off on their own to play Rambo, no matter what you read in the gunzines.)
Jim