thanks. for all the tools i have, for some reason, a pitch gauge has never been a priority item to obtain. well, i have spent an inordinate amount of time over the past 12 hours looking for specialty machine screws in that thread, which turns out to be classified as 7/8-20 unef, a standard, but virtually non existent bolt size. my next thought, being the frugal [translated-cheap!] person i am....i'm contemplating adapting/altering the existing breech plug to use any one of the shotgun primer adapter nipples on the market. i did a file test on the breech plug, and it is hard, but within the range of machine-ability. drilling slightly small for maximum thread engagement, it shouldn't be difficult to do. the biggest issue would be depth for actually seating the primer adapter, and that would be done slowly and carefully.