Most broadheads are 100 grains. Depending on the spine of your arrows, you might be able to run a tip 25 grains heavier. I wouldn't go with too light of an overall arrow weight, though. For deer, stay in the 350 to 400 grain range. For bigger stuff, 400 to 450. You need the penetration and, at the lower poundage, you are going to have to sacrifice some trajectory to get it.