Interesting about the moose.
About the crown on the muzzle. If it is rounded and smooth into the rifling, it is much easier to load. The balls must also be pure lead ie: plumbers lead or better yet, is the thin sheeting they line X-Ray room walls with.
The .562" should be easy loading with a .018" to .021" patch, even if the balls are harder than pure lead.
10" at 50 yards is not a group, imho. My smoothbore 20 gauge shoots better than that by a long shot. It uses a ball .595" with a .021" patch.
That ratio is tighter, ball to bore, than a .563" ball in a .580" bore.

I do think a lot of your problems was with too loose a ball and patch combination.

If you want me to send you muzzle crown pictures and/or a short video showing loading my 58 Kodiak with .562" ball and .021" ticking patch with the 3/8" factory ram rod, just e-mail me (my profile has my e-mail address. I use a short starter having a 3/8" hickory shaft in a Moose-antler boss for the handle.
I show 2 methods of seating the ball and patch into the muzzle, as well as 2 methods of seating the balls on the powder. The "narration" is in English, however, you will see just how easy the loading is, with a good, smooth radiused muzzle crown.

The crown EVERY muzzleloading gun maker puts on the muzzle of their barrels, other than Jim Kibler and my brother, need work. Theirs are very close to being perfect.