Don't change your bit. This will only result in the horse pulling harder against you. Instead try changing up your riding. Do lots of pole work and downward transitions. Ask your horse to halt a few strides away instead of jumping, halt or walk in the middle of lines. Keep them guessing so that they don't expect to be going over the jump every time. This will result in less rushing but will take time so you'll have to be patient! Don't give up! Ask a trainer if they think a change in bits would be beneficial as well for your horse.