I use a Black Powder substitute called American Pioneer. You load it by volume, just like BP. Clean-up can be done with Hot/cold water, or with a smokeless solvent like Hoppe's No 9 (I use Shooters Choice products.)
Actual loading bulk powders like Black Powder or American Pioneer is pretty straight forward. Prep, Prime, and Flair cases as normal. I use a muzzel loader powder measurer and set it for the desired grains of volume. If you just pour it in the case it will be very loose and "fluffy" and need a great deal of compressing. I use a 30" drop tube and get around a 1/2" shorter powder column, this will hardly compress any!
For a recommended load, IN MODERN BRASS, I use 55 to 60 grain volume with the 500 grain RN by Lyman. I seat the bullet snug against a 1/8" lube cookie and crimp with the die. For Single shot rifles No Pressure crimps are recommended, (some champions like a loose fit some have a mild holding crimp.)
If you don't wish to use a lube cookie, a simple way to keep everything lubed and any fouling very soft is to slather Crisco on the bullet before chambering. (a little messy, but very effective). Some people swab the bore every shot, and some every 5 rounds, your choice.
The recoil for a 500 grain RN bullet is much much higher than the 405 gr FN and 300 grain is almost relatively speaking, pleasant.
Bullet alloy should be zero to 5% tin, no zinc or antimony, in other words 95 to 100% Lead. I think 3% tin (AKA 30:1) is the perfect compromise. If you experiment with diameter and alloy, the rifle will tell you what will be the most accurate.
My trapdoor is a 1875 production carbine and they don't use the 500 grain loading, but my Shiloh Sharps does at longer distance.
Have fun!
Ivan
