They do but with the the tippmann 98's and ft12's the detent/rabbit thing gets flattened over time when the gun is decocked, that coupled with the ever decreasing size of paint over the last few years its become more of a case that the markers need modding for the paint that we use now as opposed to the bigger ball a few years ago.
My PGP (pre2k) came second hand with nail polish in the breech however instead of three dabs it was simply painted on all of the inside of the breech. I've tried squeegies on it and as its quite a thin sheen it does not seem to want to come off so far. It works very well however and i'm still to get a roll out. As for inserts have you considered using the Python barrel compression inserts. They are only 1.75 inches long so you can run your barrel overbored while retaining the ability to match the size of your paint. I ran mine on my enmey yesterday and found I had to adjust the reg to chrono down as it added 20-30FPS to my shots. I was using the Ion to Autococker adapter so the paint was going through 1.75inch insert at .686 then through a 12 inch Lapco bigshot. Paint was bad but it handled it great!
Note, strictly speaking that's not overboring but how insert kits work
Overboring would be to use a larger insert, underboring is to use a smaller insert
The distance required of an insert is a whole technical argument, but certainly it's the first part of the barrel that affects the ball most and not the full barrel length