Manufacturers typicaly deal in thousandths of an inch. That's the way tolerances of parts are specified. Hypothetically, apart that is supposed to be an inch long may be 1.000 +/- .005 and still pass Q/C. Of course, tolerances may be tighter or looser depending upon the part.

I'd be more surprised if they answered your question with, "almost and eighth of an inch". If you asked a gun MFR what your bore size is, do you think they'd say it's a half inch? They'd probably say it's .501 (or whatever) and they probably wouldn't tell you what the tolerance is.