Help is on the way! http://www.shooterscalculator.com/bullet-kinetic-energy.php It's a bullet kinetic energy calculator.
But I suggest to put all results of calculation to game configs. It is more easy way to balance things. Not reason to re-calculate already calculated things.
Then use pre-defined shapes as multiplier. Let's say you have shape1 = 0.8 and shape2 = 1.4, and you have a flying bullet with kinetic energy = 10; then your damage = 10 * shape1 = 8; or same bullet with different shape will be 10 * shape2 = 14. Same value you can also use to calculate reducing speed of the bullet.