Stupid he says? Well, I've been called worse.
Pay a machinist to drill and tap a new threaded hole? Now why didn't I suggest such a thing? :hmm:
The nipple for a Lyman Percussion gun is a M6 X .75 thread.
Now, as any machinist would know, in order to have a quality thread, the minor diameter (tap drill) of the new thread must be as large or larger than the major diameter of the old thread.
If it isn't, the major diameter of the old thread will prevent the forming of threads which comply with the new threads minor diameter resulting in partial threads.
A M6 X .75 thread has a major diameter of 6mm or .2362 inches.
That rules out a 1/4-20 with its .207 maximum diameter internal thread minor diameter and it rules out a 1/4-28 with its .220 maximum internal thread minor diameter unless the user is willing to accept a half ass thread for his guns nipple to screw into.
I guess the user could have the machinist make a special thread for one of Dixies oversize nipples like the Dixie .270-28 or larger but taps for these threads don't come cheap and I'm sure the user would end up paying for the tap plus the machinists labor.
It also would force the user to use these special oversize nipples from now on.
Don't get me wrong. These oversize nipples are sometimes the only fix for damaged barrels so they do have a place in our world.
Yup Richard, I guess I'm stupid for not thinking of this neat way to save a barrel that would not need saving if the owner hadn't followed some questionable suggestion about retreading a perfectly good nipple hole in his barrels breech.
Have a good day.