Originally Posted by
Tweak
When I get home I'll check the barrel and FSB prints and see what the post Park finish ream diameter is on the FSB bore compared to the post Park diameter of the seat.
ETA: print doesn't state that the dim on the barrel is after Parkerizing, I doubt it is, but the seat (M16A1) is called at 0.6238" +/- 0.0005" and the hole in the FSB is 0.6249" + 0.0005" after Park and hone. Which makes the maximum allowable mismatch 0.0021". How much thickness can phosphate be expected to add?