Broadhead weight has little to do with killing the animal and alot to do with the balance of the arrow as a whole. If you shoot light carbons, for instance, you should not add excessive weight to the front of the arrow. This will throw your balance too far forward and blow the tuning off the charts. I shoot light, thin carbons and use 85gr. broadheads, so that my arrow is not front heavy. As a rule, heavy shaft-heavy broadhead, light shaft-light broadhead. Arrow length factors in somewhat too. If you use a long carbon, you could conceivably go up to a 100-125 grain broadhead. I think my broadheads are about 1 1/8" cutting diameter. That is PLENTY.