remington kleanbores are nasty[:'(] i used them with my winchester bolt action .50 and they also gummed up the bolt horribly. Accuracy also was bad with them
Try pyrodex RS, winchester 777 Or CCI shotshell 209.

I dont know sabots/knights that well, but my winchester loves a 250 grain SST or a 300 grain XTP in a knight, high pressure sabot over 110 grains RS.