Traditions PA Pellet............hmmmmm?
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I can help you to get started, here's what I do know:
No, you don't need to use only pellets. 2f Triple 7, Pyrodex, Cleanshot loose powders will work fine as well as the pellets. If you don't have a volumetric measure (that thingie that has a rod with numbers stamped on it and a tube to dump in the powder), get one at Wal-Mart. It will allow you to measure out the powder safely. Start with a 70-100 grains.
If using pellets, use 50 grain-two ONLY. NOTE: Examine the pellets and notice that there is a black side on the pellets. That side goes down the tube FIRST, facing the breech.
As far as bullets/sabots in 50 cal.: T/C's packaged XTPsabots or PowerBelts work well and try a couple different weights. If you have a 1:28 twist rate, it should like just about anything in sabots or PowerBelts in .50 cal. I would go to Cabela's.com site under muzzleloading bullets and pick out the basic sabot and lead bullet. They are made by Precision Rifle.com and work fine....cheap!
You'll have to try various powder and bullet weights to know what works in your gun. Questions on cleaning will come next. Give us a little more info on what this model is like (side-hammer or in-line). Good Luck.
Jim