Fork hits with steel ammo

If I shoot 11mm steel balls with 15mm Theraband Gold I get non stop fork hits, this seems to be almost 80% of the time. However, when I target shoot Airsoft BB's, I never get fork hits and I am becoming fairly accurate at hitting small targets withe the BB's. Shooting 11mm steel balls is another story. I am not sure what I am doing wrong. The fork hits are all occurring in exactly the same spot on the fork.