Great gun! I have 2 of them.

250gr Thor/250gr Powerbelt Aerolite/260gr harvester scorpion pt gold with mmp-24 sabot/300gr Traditions Fullbore all shoot great in my Optimas.

Powder: Blackhorn209 without a doubt.

Primers: CCI 209 Magnum

Accessories:
Range Rod
Cleaning rod
Short Starter
Powder Flask
Powder measure
Speed Loaders or powder tubes
Nylon bore brush
breech brush
Birchwood Casey Bore Scrubber
Birchwood Casey Gun Scrubber " for cleaning out the new gun"

It add's up pretty quickly but those items are important in order to shoot and maintain your muzzle loader.