Thanks for the reply, I hope to eventually do that. But for now I want to build this first one, and was trying to get some input on the Colt barrels, specifically the ones sold as replacement bbls. from places such as J&T. Reading most forums everyone says go Bushmaster, but if the Colt relacement bbls. are the same quality that goes on their complete rifles, then thats the way I want to go. Thanks again.