Green Lantern wrote:
Am I learning that ammo choice is important factor?
Not really.
If you're talking 300 or 400 foot-pounds of energy at the muzzle, a difference of 20, 30, 40 or even 50 foot-pounds can be ignored for most practical purposes.
First, unless you are shooting your victim in the back of their neck execution-style, your victim will be far enough away that the bullet will strike the target with less velocity (and thus much less energy) than when it left the muzzle.
Second, the bullet has to remain in the victim for fully deposit all of its energy. If the bullet passes through, then the energy expended in carrying it on its journey after passing through the target was not expended damaging the target.
Third, shot placement trumps both mass and energy. If I shoot you in the heart with a 25 ACP, then between tissue damage, loss of blood and disruption of the heart's electrical currents, odds are that you will die almost instantly. If I shoot you through your thigh with a 45 ACP, then if I don't strike a major artery, you will not only probably live, you might not even be taken out of the fight.
Bottom line is that anyone who tells you that this one factor or that one factor, be it bullet weight, muzzle energy, muzzle velocity, bullet configuration, etc., is all you need to be concerned with in evaluating a cartridge (for anything other than specialist work) simply doesn't know what they're talking about. Take the time to do your homework and learn the role that each factor in ballistics plays in predicting the performance of a bullet, both in flight and then at the target, so that you have a basis for making an informed decision in how to balance each of the factors when making the decision which cartridge and bullet you are going to use.