Carbon,
You seem to be making a lot of faulty generalizations.
Keep in mind that dozens if not hundreds of these pellets were loaded into the bore of a cannon. Not one or two, it's hardly an equal comparison to what we call "pellets" today.
Also keep in mind that all gunpowder is "compressed".
It's plain and simple, muzzle loading cannons are traditional guns.
Muzzle loading is about more than shoulder fired guns.
Well ya, That's not my argument.
P.S. Did I mention I own two cannons ?