energy is mass (in grains) times velocity (in fps) squared, divided by a constant. This will link you to a calculator program:
Airhog: Muzzle Energy Calculations
HOWEVER- that is muzzle velocity. The round ball is the worst ballistic coefficent there is, and drag will start slowing them down, where the pointy bullets have less drag, and keep more of their speed (and energy)
Find your bullet weight, estimated speed, plug them in, and hit calculate.