My Knight disc extreme has always got the job done; I'd get a SS barrel whatever you choose. I've only ever shot Barnes sabots with 777 and I've never had any issues with hang ups or misfires. Cleaning is cumbersome, but if you get the right solvents, clean up time gets cut in half. I reload probably every 1-2 hunts depending on how much moisture is in the air. To swap out loads, I'll pull the breech plug and let the pellets fall out the back, then push the sabot out the front. This is why I prefer pellets, way easier to swap out for a fresh load. I've heard too many horror stories from guys who load it once and hunt for a week or two straight; that kind of laziness will cost you eventually. It's dangerous as well. I have a bud who did that and he never went back out again that season. He forgot it was still loaded the next yet and when he went to shoot it the first time he put in a primer to burn up any leftover oil residue and BOOM!
Just make sure to read your owners manual and follow what they recommend.