Got to the range this AM, and results were..... quirky.
I loaded the .45 Colt rounds in and reassembled the revolver, then began to shoot rested at 15 yards. The black circle is about ten inches diameter. Shots went higher than with the 30 grain BP powder&ball load, using these Magtech Cowboy Action loads. Clean burning, and a shorter sharper recoil impulse is responsible, I think, for the fact they shoot a few inches higher than the cap&ball loads. Grouping was good. One chamber would not fire, even on repeated attempts. Pulled the cylinder, and saw very light FP strike. Bummer.
Loaded it again, and this time two rounds got the light FP strikes. Visually I can see no difference between the affected firing pins and the ones that worked. Cylinder rotation was rough too, I had to finagle it and rotate by my off hand to get the chamber to line up. Unloaded it works fine. Some rounds were dragging their tips, some were okay.
So, it looks like this cylinder is going to need some work. I'll get a magnifying glass on it, and see if there is something I cannot see with my eyes only.
I will inspect the cases and remaining ammo too. Maybe deep seated primers?
Here's the gun with the .45 Colt cylinder on top ("Civilian Model" with nickeled back strap and TG), and the regular .44 "1851 Navy" with brass back strap and TG on bottom with it's cap and ball cylinder.
Here's the Civilian Model broken down for loading, with the two-piece .45 Colt cylinder.