I have a Pedersoli Gibbs and plan to take it out again this month as it has been resting since I built up a chunk gun and several slug guns also. Here is what I found out about mine. I tried a Creedmoor 540 grain BACO grease groove and also a 560 flat side paper patch from a custom mold and finally settled on the mold Pedersoli sells for that rifle as their bullet shot less than 1 MOA at 100, 200 and 300 yards (max distance at our range). I used 60, 65, 70, 75, 80, 85, 90 and 100 grains of Goex FFG and found 80 grains was liked best. I tried a 030 and 060 fiber was and found 060 worked best although NO wad was about as good with the Pedersoli bullet?! I found I did not like the Pedersoli tang sights so I bough a set of Lee Shaver with Soule eye piece which seem to work better for me.
I measured velocity and found 1440 FPS with 90 grains of powder and the paper patched bullet. 1395 FPS with the others and Doug Knoell's bullet lube. The bullets are sized so they just slide down the barrel as designed and all are pure lead. I tried several alloys (forget what) but they tumbled and made really BIG holes in the target. I worked with this rifle and a copy I made at the same time with a Green Mtn. barrel and except for the bullet the loading was the same.