Are you measuring from the same spot every time?
Are removing the factor of endshake by either measuring with the cylinder held forward or held back?
An uneven cylinder face seems most likely.
That would be my guess alsoAn uneven cylinder face seems most likely.
It would be really interesting to shoot some rounds over a chronograph and see if that larger b/c gap is causing any noticable reduction in velocity. 5 rounds per chamber should suffice (so long as you can keep track of which shots are from which chamber).
Par for the course these days with revolver manufacturers. You'd be lucky to get anything less than .006" gap with any current production revolver under $900..011 is a big gap.
It would be really interesting to shoot some rounds over a chronograph and see if that larger b/c gap is causing any noticable reduction in velocity. 5 rounds per chamber should suffice (so long as you can keep track of which shots are from which chamber).