His threads are precisely RH 9/16 x 24 class 3A. He started using this thread when he originally designed his tango rifle, because of the smaller barrel contour. He wanted to have more shoulder area than the ⅝" thread would provide for a varmint barrel. I have 2 barrels threaded that way to use his tac 30 can. The increased shoulder contact ensures dead center squaring, and also doesn't bite the aft end of the can, so it doesn't bind on. It fits on snug, but not so tight that you cannot unscrew it. Had this happen with my 338 can on my sako trg42.