I use Pyrodex P in my .36 with number 11 Remington caps .375 balls. Making my own balls now for the .36 and .44 sooooo.. easy and cheaper. The price of factory balls has risen dramatically, once you have bought your mould, laddle and pot your away.
The load I have settled on with the .36 is 18g by volume i.e. from flask and 18g nozzle. You could get a brass measurer from Kranks and experiment, I think 18 g is about right for 25 yds anything over 22g is pushing your luck.
Now 777 about 25% more powerful than Pyrodex P and real black powder, volume of Pyrodex P equates to the same as proper black, I use 24g 777 in my .44 - this seems to prefer 777..
What you may find with Pyrodex if using a lower amount by volume 15 - 16 g there is a slight delay - I did.
Regarding cleaning I was told that Pyrodex was a pain in the neck and more corrosive - which it is. I clean both guns within about one hour of use, and never had any problems with rust - DON'T LEAVE FOR THE NEXT DAY.
Regarding price of 777 last tub I bought was about £36.00 first tub I bought of this was about £19.00 - about x5yrs ago. Now Pyrodex not sure of exact price because I was given a few tubs by guy's packing up, I think its about the £20.00 mark.
If sending away to Kranks don't forget some spares i.e get a few hands, trigger fork springs.
End of ramble mate, safe shootin and enjoy.