there is so many companies making upper in 6.5 Grendel 458 socom and 50 Beowulf like hanover armory francis armament radical firearms Anderson to mention a few the companies that I know do not make these cal. like colt bushmaster stag arms armalite rock river what companies should I avoid the ones listed and others I going to use a quality lower stag arms bushmaster or rock river any information would be helpfull