Whats the best slingshot ammo for squirrels and pigeons

Do you shoot lead or steel 11mm or one of the smaller diameters We get techie and bring out the ballistic gel, so Wayne Martin can solve the problem of the best ammo for birds and animals. For Wayne s catapults, go to For Phill Price s airgun pellet test on this ballistic gel, go to Join the Fieldsports Nation and fund our fight for fieldsports in the media