personally i think CVA makes a pretty accurate muzzleloader. it just took me sitting down and listening to people who know better than i (when i first started i put 150 grains of powder down the barrel and went from there) and just preactice. learning your weapon. i know i can shoot better groups than the inch and a half two inch groups i shoot, and shooting the gun even more will help. on a different note i read in a black powder magazine/book (don't remember which) that 45 caliber muzzleloaders are a little more particular about loads and charges than 50 caliber muzzleloaders. not an excuse for bad groupings or defense of a gun maker, just an observation.
but with a scope you should definitely be shooting tight groups. so all i can say is keep practicing and experimenting and you will find what works eventually.