I would recommend Goex and or Pyrodex trying to shoot 777 with #11 cap only works for some people.
Pellets are designed for inlines with strong ignition systems, it is not a good idea to put them in a traditional gun.
The 535 and 18thousands ticking is a good idea, if you must shoot 530 and thinner patches look carefully at the patches after you shoot if they are blown apart or burned then your combination is to loose or your barrel is rough.
If it does not want to shoot your patch and ball combo then you might try putting a piece of linen paper around the ball. Lee