I hate to rain on your parade, but tapping out a screw thread because you don't have the proper die, or lathe lore to make a proper screw threaded to fit the existing threaded hole is not craftsmanship. The English used BA threads, and dies to cut those threads are available in this country.
Now when an SAE thread is cut to expedite things, what happens should the gun find it's way back to the UK and for some reason needs a new screw? the gunsmith called to do the repair wonders what the "new" thread is, he either must make a new SAE screw, or maybe using the "easy way' logic, drills it out and retaps a larger BA thread in the hole, now the threads may larger than the screw shank. I just think it is not ethical to retap holes to a size you may have, unless it is necessary. Proper tools are available, an internet search should bring them up.
And, the original screw was case hardened for strength, is the replacement?
