Yes, these are some additional good points. People tend to think that a .32 caliber rifle is a .32 caliber rifle. Well, in one sense, that's just an instance of a law of logic. But what's CALLED a ".32 caliber rifle" may be a .31 caliber rifle or a .32x caliber rifle, and barrels may differ significantly in terms of the depth and shape of their rifling grooves. I think this is especially true in the black powder realm. But it's not restricted to that.
I have a wonderful CZ 455 .22 heavy barrel rifle that I use in precision small bore shooting. Except you can't actually get a .22 cleaning rod in it! One of the ways the accuracy is squeezed out of it is that the bore is actually .21-ish. So when I use a cleaning rod in it (which I don't often do), I need to use a .20 caliber rod. The same was true of the CZ 452 that preceded it (and which I wish I still had).
And another thing to consider with regard to accuracy is the sights -- especially for those of us "of a certain age". After my "cataract" surgery my eyes are much improved (in fact, I haven't seen this well since I was 12 years old!), but sights and sighting picture are still very important. I found the Crockett rifle standard sights to be VERY accurate -- IF I could focus on them to get the correct sight picture consistently. But with the small (square notch) rear and the tiny front, this was difficult and irritating to sustain. I replaced the rear with a full buckhorn (with a square notch in the base) and a taller and more visible front (silver) blade, both from TOW, and it is now much more comfortable to shoot and to shoot consistently. This sight set-up is also much better for the 25/50/100 yd matches I typically shoot since it gives me more visible, distinct, and consistent sight pictures for the different distances. I've "slightly modified" the buckhorn for this purpose (adding some index marks to it).
Finally, I find that for repeatable accuracy I need to be very careful not to cant the rifle as I'm sighting/firing. It's easy to do this and somewhat difficult to detect, even if you're sensitive to it. But it can really open up groups, particularly at longer distances. On my CZ, there's a Vortex level attached to the 6-24x scope, but (even if I could figure out how to do it) I don't think I'd like that on a muzzle loader.