I think your concern about stresses induced by the threading is a valid one but I certainly can't quantify it. Can you, mathman?
I've seen video where the opening of the ID was demonstrated with close fitting precision pin gauges. On the small OD threaded samples the close fitting pin slipped in the muzzle and always stopped at the end of the thread seaction.
So it's a "deeply recessed crown"! It's a FEATURE!
