intoodeep,
You've probably read the "10 gauge cannon? Can someone school me?" thread Started by DukeInMaine already. I'll be frank, I've always just assumed (maybe wrongly) that all signal cannon had straight uninterupted diameter bores, from the Strong, Brown, Snow etc. guns of the early 1900's, all the way up to comtemporary models made by companies such as Beaufort Naval Armorers. Does the bore of your newly acquired Brown 3 Ga. show the same diameter at the breech as it does at the muzzle, and is the diam. measurement uniform all the way down the bore?