Re: GAP vs CCR vs McWhorter
I know a guy who had a 7mm Rem built by McWhorter (he's on their testimonials page), and a 338 RUM built by CCR. They are very similar rifles and both shoot very well. He has no complaints about either one, and picked CCR for the 338 because they were less expensive but the components were essentially the same.
I wouldn't hesitate to use any of the three you mention.