KBacon: My gun (Encore) will shoot certain combos of powder and bullets, and absolutely reject others. For instance, my groups are with 3 pellets (50gr) triple 7 pellets and a 250 grain shockwave bullet. However, seat a hornady 240 xtp on two or three 777 pellets and you get a shotgun pattern. But the xtps will shoot fine with loose pyrodex[&:] It's all about finding the components that play well with each other....
Although I just started using the stuff, real black powder has suprised me in it's accuracy and consistent performance. If you can find some GOEX, give that a try. Like your father said, "have to clean the rifle regardless"