I am a recent addition to the Evil Black Rifle Club( and it IS evil, when I get it out my dog runs away in fear!). I know a little about them. I can shoot and field strip my AR but that is the end of my experience. I am much more familiar with M-14's, 1911A1's, M-79's, Rem 870's, M-60's and M2's. I know that you can get different style uppers for them. I currently have a 24" .223 heavy barrel and a flat top upper. Nice for varmint type shooting but not exactly Service Rifle competition or 3 Gun material. I would like to put either a 16, 18 or 20" upper on it. I want to end up with an accurate military appearing rifle/carbine that I can use in 3 gun or CMP matches. I want to stay with .223 or 5.56 NATO Questions. Do I have to buy a new bolt& charging handle or can I reuse my current one? Will all uppers ft my Eagle Arms lower receiver? Will M-16 uppers fit the AR15? I have read that firing 5.56 in .223 chambers causes an overpressure condition. Is this fact or fiction? Should I go with a .223 upper or a 5.56 upper? What should I expect to pay for a Complete upper? How about one w/o bolt and charging handle? Where would a good place to buy and upper be? Gun show? Auction Arms? Gunbroker? Anything that I forgot to ask that I should have? Thanks, Guys.