I've been talking with Sabotloader about my Knight Disc Extreme. I have an extremly (no pun intended) tight bore! Loading a 300 gr .452" XTP in a black CR sabot takes all of my 215 lbs while a 250 gr one is somewhat easier. 290 gr Barnes TEZs with the supplied sabot is next to impossible. But using the Harvester CR sabots they load pretty good. At Sabotloader's advice I ordered some of MMPs 3P sabots. Hopefully I'll be able to use them with the XTPs for sighting in and general plinking fun. Then resight in with the Barnes for hunting.
I think when I get back home I'm going to give the bore a good polishing which might make loading a bit easier. It definitely will help reduce cleaning time.