Got an e-mail from CPA.

[drcook]

I put a turn or so of thin teflon tape on the threads. You just have to experiment as to what snugs it up/provides some wear protection -vs- being too tight and preventing you from turning them in by hand.

I have a couple CPA's that have multi-barrel sets and show no wear on the threads. There are a couple that the teflon embedded itself into the machined surfaces of the threads, similar to how Slick 50 embeds itself into the metal parts of an engine.