I have a Trapper also. It's a very good shooting gun. Remember, each gun is different and has its own preferances. My gun's favorite load for accuracy is 20-25 grains 3F for a .490 round ball on a .015 patch. Yours may differ according to lube, etc. I'd suggest starting at maybe 15-20 grains and working your way up a grain at a time till you find the gun's sweet spot. You'll know it because your groups will tighten up dramatically.
I hope you enjoy yours as much as I've enjoyed mine. BTW, locktite the 2 trigger adjustment screws! There's one between the triggers, and one just behind the rear trigger, under the trigger guard. They have a habit of shooting loose and that can lead to a dangerous condition where the gun can go off without you pulling the trigger. Learned that one the hard way.