640 no dash with about 200 rounds fired. It has a .007-.008 gap. Is that acceptable BC gap? also should it be measured in its natural state or with the cylinder pushed forward?
I checked a couple of my new 442s and they were.006
Thanks in advance.

If your end play is less than a couple thousandths, I would not worry about that .008 gap. You'll find up to .010 gap that shoot fine. The gap is measured with cylinder pushed back.
If you have excessive end play it should be fixed.

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Science plus Art

It has .001 endplay. What is the fix for excessive BC, and/or endplay?

0.001" endplay is nominal and normal. If a lot more than that, it is corrected using crane end bushings (washers).

Excessive B-B gap is corrected by setting the barrel tenon back one turn and refitting the B-C gap.