okay the title was a little misleading. anyhow, I was doing a little math on muzzle energy vs. momentum while deciding which rounds would best compliment my new p2000. I only use these numbers as an example: hornady 155's vs. cor-bon 135's in .40 s&w. 155 has a lot less kinetic energy, but much more momentum. I was thinking the lighter cor-bons would make a better round for warm weather where an assailant would be wearing a t-shirt, and the hornady better for winter where one would most likely be wearing heavy jackets or multiple layers of clothing, as the extra momentum would prevent it from decellerating as quickly. both should work fine but any thoughts on changing out the mag when the weather calls for snow?