Stick with lighter loads, and work up from there. I am talking about 12 grains of 3Fg powder, and then work up to 15, 18, 20, 23, 25 grains of powder. I know some shooters who load up to 30 grains with a PRB, but that is the exception. Most are shooters use 20 grains for a hunting load, and target loads are less.
I have an original .32-20 cartridge rifle and that cartridge shoots a 110 grain bullet in front of 20 grains of 3Fg powder. The ROT on the rifling is faster, than on your gun, so you are restricted to using the lighter, SHORTER, bullet. Look for small groups, and adjust your sights later to zero for that load.
Most shots at turkey are going to be under 50 yards, and I think you would be asking a lot of your ability to shoot iron sights, as well as the accuracy of the ballette in hunting weather conditions of you were trying for a head shot at much more than 50 yds.
Those light balls do drift on even light winds, and that is the real reason that You chosen hunting range needs to be restricted, using either RB, or these short conicals.
You can kill a turkey with a body shot, but it may still be able to fly off and die out of your sight. That is a lousy way to kill a bird you can't retrieve.
Accuracy with that conical will depend on the depth of rifling in your barrel and its rate of twist. The bullet should be sized to within .001 to .002" of the bore diameter. If the grooves are more than .003" deep, you probably should use an OP wad, or filler between the powder charge to protect the base of the bullet, and seal gases behind the bullet to prevent gas cutting of the soft lead. You want the release of the bullet at the muzzle to be clean and even all around the circumference. Otherwise, gases escaping from one side or another early will cut the base of the bullet, and destroy any accuracy you might have gotten.
That weight of bullet is more than enough to go right through a Turkey's neck, head, or chest. The neck or head shot is preferred to anchor the bird DRT.
