This Radical Firearms RF 7.62x39 M16 BCG, Melonite Bolt Carrier Group will not work in a 50 Beowulf Upper. From what information I have found the 50 Beowulf uses a similar bolt face to the 6.5 Grendel but uses a different extractor. So that means it is best to get a 50 Beowulf BCG which we currently do not have.