Right now, I have a Bushmaster AR-15 with the "16 upper, A1 style sights, and trapdoor buttstock. I am thinking about buying a "20 upper, with A2 style sights. I want the better sights, and from what I hear, the ballistics of .223 are better out of the longer barrel. I also want the true military look, and maybe a little bit better accuracy. I have a few questions about doing this swap ( I would keep the "16 upper). If I buy a new upper, should I buy a new bolt/carrier/charging handle, because of wear or fit? Would this be cost effective? I have the 2001(I think) Bushmaster catelog, and it has a national match "20 upper with bolt carrier assembly and charging handle for $525. Or the same thing with out bolt carrier assemble and charging handle for $385. Thing is, I spent $600 on the gun-used from a good friend, and that would be a lot of money just to basically change barrels. I know actual prices would be lower, but probably not much. Should I just save up and buy another AR? Any info or opinions would be helpful.