Per the Kuhnhausen’s book, industry revolver barrel/cylinder clearance specification is .006” for jacketed bullets. Some lead bullet bullseye shooters set clearance at .008.

.012 seems a bit excessive. How is the yoke to frame fit? Does the yoke rocks form side to side you apply side to side pressure with the cylinder is locked? I would check that, in case the wrong yoke screw was used or if it’s damaged.

Cheers,
686PC