100 grain is the best. Different grain heads are not made just for shopping pleasure. They are made to match the arrows weight and spine. Sometimes you can error on the heavy side and still be OK though. If you go with to heavy of a B-Head and a real light arrow you can really affect your FOC ( front of center) balance. Most all CB guys shoot 100 grain heads, but there are some guys that shoot 125 with no problems. Most CB makers recommend 100 I think, but if I remember right Barnett was 125, but not sure which arrows they use. But like I said, the different weights are not out there for the heck of it, start drifting to much and you can have problems.