Found a less expensive way out. Buy a DSI fixed magazine lower that will take my existing uppers. As it cannot "receive" a detachable magazine. As it is no longer "an assault rifle", I can keep all the evil features. The 223 & 300 B/O go right in the magazine and an adapter will make it work for 450 BM.As the magazine comes apart from the bottom, it can be blocked to make it 5 round legal for hunting.
http://www.dark-storm.com/dsi-ds15-asse ... e-blk.html Thanks for help and advice (unlike some other sites, which are full of misinformation)