Home Forums Hunting & Shooting Gunsmithing ithca model 37 barrel fitting?

have a model 37 with 2 barrels. original and one that needs fitting. it is about 1/6 of a turn from rotating into firing position. If I trim barrel face and shoulder the same amount until rotates to 0 degrees and check headspace . is this the method or am i missing something? used to have a factory directions but cannot seem to find.