I would be careful writing off prefits. I will say its a bit more of a gamble then buying a blank and having a good smith chamber it up for you but most of the time I haven't seen a difference. I have full custom remmys and pieced together savages and sure, the remmys feel a hell of a lot smoother, easier bolt lift etc. but more accurate? nah. Maybe I got lucky with my CBI being as accurate as my Brux though...

Also if your reaaally serious about winning some matches you're probably already running a surgeon/bighorn/stiller/defiance etc with a custom tube so this is a moot point anyways.