I just love this one:

Momentum is the better predictor of penetration ? and SD is not?

Sorry but I strongly disagree !

Momentum by itself says nothing about penetration in a medium, short and simple as it does not address the retardation forces that the medium exerts on the projectile !

A 150 gr monometal, non deforming, non fragmenting 30 cal projectile shot at higher velocity does not outpenetrate a 220 gr monometal, non deforming, non fragmenting 30 cal projectile shot at equal momentum values, not at the maximum allowable velocities for our current ballistics systems !

Retardation as a factor is dependent on projectile mass and projectile frontal area, in short related to what we commonly refer to as SD.

The variuos penetration models that exist such as Poncellet all employ momentum but in addition to the mathematical calculation of Retardation ! It is a ballistics principle as old a man itself !