Plinker, or can I call you Farm?
One of the problems with flinters is getting them to ignite with just a spark. I do not know much about 777, but FFF ignites easily with just a spark. If you read a bit, you'll see that it is just as easy to clean up black powder if you use the right lubricants and never put oil to the barrel.
I do believe that pellets will not work.
Always remember that gas does escape from the touch hole - never shoot with someone standing in front (to your right) of it.
Good luck with what ever you use.
C F