My M64 was worked on in the Performance Center last year. I had them remove the old 4-in barrel and install a new 3-in barrel which I provided. The work was spotless - no added marks or scratches. The B/C gap was set uber-tight and lockup was just as tight as when I sent it in. Their statement of work did not mention it - but I'm convinced they also blasted the top of the frame because it now looks like new ...

Understand this isn't really on-topic - but I was/am very happy with their work for $90 + shipping...