Og made a suggestion

Actually two, but I decided to try one. Yes, I may try the other later, too.

You want to know how great this friggin' country is? I can go to Ace Hardware to get music wire. And while I'm there I find they have 4x40 taps. AND 4" pieces of 4x40 threaded rod. Which producedYou can't really see in the shot, but each has a side hole drilled & tapped, and a short piece of threaded rod as a setscrew. With a slot in the end for adjusting. From left to right the pins are .120, .092, .078 and .062. I need a .100, but they didn't have that size wire and I didn't take time this evening to turn one(but the body is ready).

I did discover something while doing this: had both holes drilled, ready to tap the one and my tap wrency is gone. Vanished. I actually have two of the damn things, and neither one could be located, so I used the drill press. If you've never tried that, you lock the tap in the drill chuck, get the hole centered under it, use just enough pressure to lower the tap and turn the chuck by hand. For small holes it works well, and keeps the tap square to the hole. Which also reduces the chance of breaking the tap, especially on a small one like this. If I were going to be doing a LOT of these, or something similar, I'd go to Brownell's and get this rig; uses the press to keep it straight and don't have to turn the chuck.

I also found that, while using the lathe and a bit to face the ends of the body is fun, for this I can do it quite nicely with a file. Center and lock the piece in the chuck, and while it spins use the file to square it. Since one end is going to be whacked with a hammer, and the other is going to have the center cut with the lathe, it speeds things up a bit.