I played with 777 when it first came out, then gave it away after using about 1/4 of the pound. I believe a good quality black powder is superior to any fake modern powder that has something thrown into the mix to make it smoke. They suck.
My experience is that you can have a rifle that's sighted in with a warm fouled barrel, or a cold clean barrel...but not both. I'm a hunter first, and a shooter second, so this is what I do: I clean my barrel between shots when sighting in. Not a full and total cleaning, but I wipe out the barrel quite well...not just one or two wipes. It's kind of a long process, but I do it on a nice day, enjoy the outdoors, just take my time, shoot and clean the barrel, and watch the world go by.
But I know that's "too much" work for many guys. However, it works, I like hunting with a clean rifle, and I believe a clean rifle (or smoothbore) is more reliable than a fouled rifle. ESPECIALLY a cap-gun. Anyhow, my first shot goes where it's supposed to, if I do my part.
The other thing is, in my experience, and I don't fully understand this, is that subsequent shots (one or two) are not as far from the clean barrel shot, as the first shot from a clean barrel is from the POI when the barrel is sighted in with a fouled barrel. (or visa-versa) ??? Did that make sense?
Again, we're not cleaning the whole gun with soap and water and rubber duckies, just running a half dozen or so patches wetted down with a good water-based cleaning solvent. Then a few more to get the barrel good and dry. That will replicate a clean barrel. I like "Blue Thunder", but I'm sure there's a million others, whatever your preference is. I suppose even a small container of soapy water to dip the patches in would be fine, especially if it had a rubber ducky in it. You just don't want to get breech or powder chamber wet.
Anyhow, just as idea. Works for me. Not gonna work for the target shooter, will work for the hunter. !!!