Thanks, gents.
Splinter - I had the same thought about using the HDPE tape to reduce wear at that point, but also realized that it would reduce friction where I wanted friction, so I didn't bother. I also thought I could put a thin veneer of the same ash over the end grain of the plunger if needed, if it's getting worn or causing wear on the cam. I can always replace the parts, too. I'll just wait and see how they hold up before I solve a problem that may not exist.