Well, I have a different take on that conversion; Mine is a Bushmaster Upper matched with a Colt Lower bought as a whole gun about 10 years ago. It has been reliable, accurate and a pleasure to shoot. I did have to buy some "C Products" mags for it to have more than 5 shots. I have put at least 5,000 shots thru it shooting 3 gun matches, Whitetail Deer, and steel targets at 300 yds just to hear them ring. I think that it is an excellent cartridge in an excellent semi-auto rifle. Did I say that it has been reliable? I haven't had a lick of problem with it since NIB. And it is dead easy to reload for. ++++++++++ ........... Big Cholla