Let me just chime back in here. Yondering and gnoahhh, I am a fan of both of you, and I've taken both of your advice over the past year in my quest to do cast bullets.
I cannot say if there is or is not barrel wear. What I can tell you is that I did see some people on the various forums I haunt mention barrel wear. I think some folks saw a hazing of otherwise bright bores that they attributed to abrasion. Whether or not this is accurate, this comes from a minority of people trying the powder coat method. That hazing could be a bunch of things.
Hypothetically, there might be abrasion. However, it probably would not come from the polyester base, but from the colorants. Yondering, you pointed me towards a green paint. I found out the main ingredient in the color agent is Titanium. Running Titanium-impregnated paint down a bore? I dunno. However, it has not stopped me. If I do find my barrels getting hazy, I may change my mind, but I have not seen it yet.
