Is it a reasonable desire for a relative amateur AR-builder to attempt to assemble a 1/2 MOA or better AR-15 from quality parts? I have finally broken down to the point where I want to make one to cherish for myself (not to be resold) and was looking at getting a CLE barrel and matched bolt, and I know that a tight-fitting receiver combo (and all parts really to ensure that the rifle doesn't shift around internally at all from the vibrations of the recoil impulse) and match trigger are needed but is there anything I'm not seeing that a gunsmith's involvement makes or breaks the rifle? I get that you wouldn't be able to check parts for tolerance but with good parts could you avoid that nearly entirely? If it is possible, what components are important and who should I look to when choosing them?