All ARs are built from parts.  The important thing is the QUALITY of those parts.  Parts quality is not always *visible* or easy to measure or identify, especially it you don't look at these parts every day.

Generally, the less you pay for parts, the lower the quality of the base materials, the more machinging and/or heat treatment steps were skipped to save money, and the fewer quality-control/quality-assurance steps they've gone through.  In other words, you usually get what you pay for, and when there is an exception to that, it's usually you getting LESS than what you paid for, not more.

Just something to consider regardless of who you buy your parts from.

-Troy

There are a lot of things that can affect how accurate an AR is, but some are way more important than others.  Start with a quality barrel and a fitted bolt, then freefloat it. If you are satisfied with the result, call it good.  If not, my next stop would be the trigger. After that, a lot of practice with the particular gun until I learned more of it's particular nuances.  Then you can think about other tweaks that may or may not have any measureable effect for your particular shooting style.

There are lots of things that people try to make ARs more accurate. Books have been written about the subject.  Virtually everything can help, but the basics are barrel, bolt, forend and trigger.