By definition from physics, momentum, and not kinetic energy, is the correct formula to measure the directional (in this case, forward) "impulse" of a body in motion. It is the force exerted over a period of time in one specific direction, ie: a unidirectional force vector.

Kinetic energy (K.E.) is scalar, or nondirectional,in nature, and includes all the types of energy of a body in motion. K.E. has no direct bearing on penetration. A tuning fork, once struck, has high kinetic energy (it can shatter a crystal wine glass), but has almost no momentum. It would makes a darn poor penetrator of tissue!