Possibly a quick loader for a large (4 or 6) bore single barrel muzzle loading shotgun? The capped tube would hold the pre measured powder charge, the hole in the end would work for a neck lanyard. Wads and shot flask would be carried separately. I said a single barrel because I can't imagine anyone having just fired a 10 or 12 Dram right and left would want to quickly fire a third and fourth.
