Trying to shoot "pellets" in a conventional ML is probably a waste of time.
You must be very careful playing with binders and such. Adding things to propellants can be a *big* mistake.
First it plays with the burn rate of the propellant. BP is a surface burning propellant its burn rate is largely controlled by grain size. In guns shooting RBs the burn rate could be too slow to produce good velocity regardless of charge weight unless the pellet breaks when the pressure increases.
In cartridges this can be made to work and perhaps in inline MLs. In a conventional ML the breeching relies on the powder grains getting close to the ignition source. With a solid pellet this is impossible.
Compressed pellets of powder were known and used prior to our Civil War. Powder for large cannon was not granulated as is the blackpowder used in smaller cannon or small arms. It was formed into grains during the pressing stage. Some of these were the size of small apples.
This was done to try to control breech pressures in Naval guns using heavy projectiles and huge charges of powder.
The 303 British cartridge originally used a compressed pellet of BP with a hole up it middle to promote burning. But a 303 cartridge is not a ML. Greener's "The Gun and Its Development" has a wood cut showing BP pellets.
If you need more performance use Swiss powder.
The paper cartridge is a good way to rapidly reload a rifle or smoothbore for a faster second shot. I do not believe it is practical in the rifle for "normal" use.

Dan