My friend shoots the same Cabela's rifle. And all I can tell you is, his shoots roundball perfect. If the patch is being destroyed, I would suspect either they are very old patches that were pre lubed. Or the barrel is rough inside.
I would take some JB Bore Paste and work the barrel over real good first. Then get some cotton pillow tick and lube the patch right before your ready to shoot. 80-90 grains of 2f powder should work fine. If you can't find black powder, try Pyrodex RS.