to calculate momentum, multiply bullet wt in grs, by velocity in fps, thro out the meaningless zeros. 21.8 momentum factor for such a .45. A .45 has 4x the frontal area of a .22 centerfire, like the 223. A 70 gr sp, at 3100 fps in a 22-250, has less momentum than does such a .45. Yet the 70 gr sp is MANY times more effective at dumping a big dog on his ass, anyone whose ever used such a load knows that.
So the momentum-frontal area" stopping power calcualtion is all WET, when one reaches 3000 fps or so in velocity. Even COOPER says that at 2200 fps, velocity and shock-transmission mean FAR more than does bullet diameter and momentum.
in fact, Jeff said that a 40gr .22 spitzer, at 2200 fps,could both penetrate any practical body armor, and still have adequate stopping power, by means of HYDROSTATIC SHOCK.
Well, my POCKET gun load has 2.5x the frontal area of a .22, and 36% more bullet wt(than the 40grs Jeff stipulated, and it's 2200 fps.
So the momentum-frontal area" stopping power calcualtion is all WET, when one reaches 3000 fps or so in velocity. Even COOPER says that at 2200 fps, velocity and shock-transmission mean FAR more than does bullet diameter and momentum.
in fact, Jeff said that a 40gr .22 spitzer, at 2200 fps,could both penetrate any practical body armor, and still have adequate stopping power, by means of HYDROSTATIC SHOCK.
Well, my POCKET gun load has 2.5x the frontal area of a .22, and 36% more bullet wt(than the 40grs Jeff stipulated, and it's 2200 fps. 
