Bore butter is just fine for the Patch and ball situation it was designed for; It does not do well with sabots. Sabots are designed to be self lubricating and while you need to lube your barrel with something [I prefer Montana X bore preservative or Birchwood Casey synthetic oil after you scrub it.
Power belts can be made to work but are on the bottom of the majority of the well experienced shooters lists because of the fact that with a load that gives good terminal results [80 gr or less] you get a rainbow trajectory.
Now in some states you must use conicals if thats the case I recommend the Thor and the FPB [Hornady] Other wise I would suggest trying the Shock Wave which usually works quite well in that gun, with 110 gr. You did not say what powder, if your budget is tight use Pyrodex if you can afford the best try Blackhorn. APP is weak and gathers moisture and 777 will give most people a crudring that takes considerable scrubbing between each shot in order to maintain any accuracy.