My fiance has bought too many lowers and as a wedding present I want to get him some AR uppers. He prefers odd caliber uppers. He already has the 6.8 something. If anyone has 9mm, 7.62x?? something(he shoots it out of his AK?), .22 or a 5.56, he says it's a .223/5.56 but he wants to make sure it...