Gunsmithing Tikka Barrel threads-metric?

The 18x1 mm is the brake threads. Skeetlee, i have had two done by Brian Wick in Albion,il. One was a tac with the metric brake threads but the action/barrel threads are 1" 16 tpi. That was his first tikka build and he assumed, like me, that it would be metric since the brake was. The second one was also 1" 16tpi. Either way he wasn't too worried about threading metric, he turned a 1/2x28 ops inc brake to 18x1 mm so it would screw on the factory metric brake threads.
 
I should clarify, he did the brake rethread 1 yr before the rebarrel. He also trued the receiver face back to the flats, that way i could run a 1.2" lv contour. If that taper is left on there the biggest u can run is 1.10. The first action was dead nuts on with minimal lug lapping needed to get full contact. The second one had a little more contact on one lug than the other