I hunted with black powder shotguns on a regular basis in the 70's and 80's. It was my dad's passion, he was a collector of anything old having to do with waterfowl. Almost all my experience duck hunting with BP is with breechloaders, both hammer and hammerless. I have very little experience with muzzleloading shotguns, quite a bit with rifles. We loaded our own ammo for the most part although there was one manufacturer of 12 gauge back in the 70's, the name of which escapes me. Loading for ducks was painful because they needed to be roll crimped, or hot waxed atop an over shot wad in order to cram in enough powder, wads and shot. I still have several dozen brass 12's and 10's that we used for "special occasions", which meant dressing up in tweed jackets and wellies. I hated that at the time, but it's grown on me in old age. Loads for railbirds could be star crimped because there was less volume of powder and shot. The smoke cloud in a rail marsh on a calm, warm, early fall day was glorious to behold. A fire in the grass started by burning over powder wads, not so glorious.
If I was going to do it now, I'd be excited to try TSS. What I don't know is how it effects the pressure in a BP gun. Of course, all but a few of what we had were damascus barreled so they weren't going to take much abuse. The pressure curve is quite different between BP and smokeless since BP is an explosive and smokeless a propellant., therefore I don't believe trying to equate TSS smokeless pressure curves to BP is a good idea. What I'm quite confident of, is that if the pressure is within limits the TSS will kick ass because it doesn't need a lot of choke. Relatively few pre-1910 off the shelf (as opposed to bespoke) BP shotguns have what we would today consider more than a modified choke. Most that I have used were quite open, with less than .015 constriction in a 12.
