Marks21,
Try it at 100yds and see where it shoots. Unless the gun has been changed(or maybe front sight bead broken off), it should shoot close enough with ammo that duplicates original bullet weight and velocity. Also, a drilling will "walk"(usually, up) if the rifle barrel is hot and shotgun barrels at ambient temp.
You should not rest the barrels on the front rest, they will shoot away from the rest. You should hold the drilling in your hands, like you would hold it in the field. It is OK to rest your hand on the rest, which is set high enough to sit upright.
Mike