I also have one. A sweet shotgun. Fine wood, nice locks, light-weight barrels. I'm about 5'9" and stock fits well. Owned and shot it for 40 years. Lower barrel is a problem: I used a drill bit in a hand chuck to open it up.
Tried musket cap/nipple (musket caps thought to provide more 'flame' than conventional #11 caps) Then tried super-cleaning/de-oiling flash channel with fizz can of brake drum cleaner. These remedies all worked to get 100% ignition in the lower barrel, but if you are hunting with it, be sure to do this routine before loading: snap several caps, especially on the lower barrel, and be certain you get a good flame from the muzzle. (My criteria is to sway the short grass/dried leafs at the muzzle.)