Nice upper...its a 1:7 so you should be able to shoot anything 55gr and up without problems. My choice would be a 62gr FMJ green tip. Lake City, Federal or American Eagle are good choices. Avoid the cheap bulk ammo until you get a good zero so you don't waste time adjusting for variations in the ammo itself.
"The whole of the Bill (of Rights) is a declaration of the right of the people at large or considered as individuals.... It establishes some rights of the individual as unalienable and which consequently, no majority has a right to deprive them of." (Albert Gallatin of the New York Historical Society, October 7, 1789)
"A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government." - George Washington