You must use a Hex calculator to find it out.
Rapidfire Player 2 = Rapidfire Player 1 + (Health Adress Player 2 - Health Adress Player 1)
But i think you can also do Rapidfire Adress player 1 + 57F8 = Rapidfire Adress player 2
Cause 57F8 is the offset from Player 1 -> Player 2
Hope that works!!