Is 777 even recommended for a sidelock and #11 caps? I think you may run into some problems there. In my T/C Hawken, Great Plains bullets always shot well with 80 grains of Pyrodex.
I've had excellent luck with 777 in my TC sidelock. It's been a long time, but Pyrodex always gave me ignition trouble in the Lyman GP 54 I had. 777 does, however go bad over time, at least once it's open. BP lasts forever, but can be hard to come by in some places.
Just buy enough 777 for a year and then shoot it up or spread it on your lawn.
777 gives excellent velocity and cleans up easily using Ballistol either straight or diluted 5-1 with water. Steel won't rust in a10-1 water-Ballistol solution, so after cleaning, just dry patch the barrel and then swab it good with the straight stuff. I never had any trouble with corrosion in my flintlock using this method, (with BP, of course). A couple passes with a dry brush or a damp patch will knock out the crud ring that will form after a few shots.
