My VLTOR upper has a large enough ejection port but yes a lot of them don't.Make sure it's a "big bore" upper receiver or the case/brass will NOT eject! Standard ejection ports are NOT large enough for the brass.
This is what I did.Why not a 450bm? Seems much easier
I chose the 450 Bushmaster over the Socom because of the hunting regulations that require straight walled cartridges. My only suggestion would be to use an adjustable gas block and a brake to prevent damage to the lower.Has anyone built one? My son has a dream of a big bore AR. What are the things I need to know if any?