Chuck, the problem with the nipples is they get abused by the jet of hot gas when the charge fires and also get dinged/chipped a bit as the hammer pounds the nipple against them to cause the priming compound to explode. I still think his best course of action is to see what the thread may be, or at least to define it so a machinist can cut a similar one. A permanent solution would be to have a die maker cut him a die in the thread required to fit the barrel and use it to rethread commercial nipples or nipple blanks if he can find or make suitable stocks. He might get lucky and find the thread is reasonably common. If he shoots the gun frequently it would be reasonable to have a couple replacement sets available against several years of use.
