Many gunmakers used odd sized threads .some used bicycle threads others use what we called sewing machine threads ,there were a lot of different one to choose from .
When all else fails you can usualy tap out to a close BA size in this instance I would guess at 7BA which is if memory serves is 2.5x .75 mm equivolent . Beads have been made of various material nickle silver ,white brass, brass, most Purdey beads are small so this is less important than shape and size .
Last edited by gunman; 01/20/13 09:50 AM.
