The only thing with 777 and sabots I've found, is that you usually do need to swab the bore between shots. When I shot Powerbelts, I could get away with shooting 3 - 5 times without swabbing. What I normally do is take my ramrod with jag, and run a wet patch (either spit patch, or soaked with Windex) through the barrel, then I run a dry patch. Then reload and shoot. This makes sure that no crud ring builds up, and keeps the accuracy.

However, when I'm out hunting, if I shoot- I reload right away without swabbing. This has worked fine- accuracy is still good for the 2nd shot.

Pyrodex is a good powder, and accurate - I just don't like it because of the clean up issues you have with it, plus it has a little less ooompf than 777.