Man, there's no requirement to do homework in the rain.

Does the drum on that gun have a clean-out screw. Have you taken out the screw (or the nipple) and put a light in or against the hole and looked down the bore? You should be able to see if the holes line up right.

Does it have a patent breech or does the drum screw into the barrel in front of the threaded section of the breech plug? You can open up the obstructions(very carefully) with adrill bit brazed on arod.