First off, a Pedersoli should shoot pretty well. You're probably not doing something right.
Second, you HAVE to know that ACTUAL bore size, not what's stamped as it does vary.
Third- after you know the bore size, get your bullets for testing here-
http://www.lodgewood.com/Bullets_c_7.html
Fourth- forget Wonderlube. Use beeswax/lard,crisco,olive oil in about 60/40 mix.
Fifth- try Old Eynsford 3f (Goex product) at about 40-45gr. DO NOT use the "reenactor" powder, it's for blanks and QC isn't important for that purpose so accuracy will take a very distant last place.
Sixth- good caps, RWS or Schutzen only. CCI reenactor caps are garbage for any kind of accuracy.
Some further comments, I've seen minie bullets from some commercial sources not be pure lead and were a disaster for accuracy. The vendor is relying on whoever cast them to be honest. The lead has to be pure. The link I gave uses nothing but pure lead and he's an NSSA competition shooter as well. He knows what you're going to need and he makes quality bullets.
For what it's worth, there are many in the North South Skirmish Association who know how to make a musket more accurate than you can hold. If you're in the eastern US, see if you can get to a Skirmish and get to know some of us.
One last comment on testing method, if you are bench resting the rifle, have the portion of the rest holding up the rifle at about the location your forward hand would be. This is due to how a musket acts during firing. If you rest it near the muzzle, accuracy can suffer and it WILL change your Point of Impact on target. Also, be consistent. Change one variable at the time.