Couple things to note:
The total kinetic energy is NOT just it's linear velocity (E=.5*m*v^2) but you must add its rotational energy also (E=.5*I*w^2) where I=moment of inertial and w=angular velocity. So with no way of determining the angular velocity (rate of spin) you can't accurately predict/calculate the total kinetic energy with just a chrony.
Momentum has more to do with how hard the bb's will hit (M=m*v) and isn't related to kinetic energy. Obviously a 25% increase in BB weight (.20-.25) does not result in a 25% decrease in velocity, therefore more momentum is present.
I can't comment on any empirical evidence (as I have none) but this is my knowledge of the theory.
Last edited by Flatlander; July 10th, 2007 at 13:04..