I think it's important to at least try to understand the ballistics and physics being addressed in this discussion, but it probably becomes more important if you're using a rifle on a distant target than a handgun on a target up close and personal. I'm not trying to downplay the importance of this discussion, but wonder the self-defense/home defense concerns might push this discussion in a different direction if hunting (and rifle velocities) is not one's primary concern.
Much of the materials presented in the various excerpts and references address rifle bullet performance at great distances. This is a handgun forum, and while some here (I don't know how many) do hunt with handguns, many are arguably more interested in handgun performance at self-defense and home-defense distances. I think we might be talking about what are two basically different subjects (even though the ballistics apply to both types of rounds).
In the reading I've done, which has been mostly focused on the rounds used in CARRY weapons, it seems that WHERE YOU HIT YOUR TARGET -- (placement -- IS A KEY CONCERN and PENETRATION IS CRITICAL. That penetration must be sufficient to hit a vital organ, major bone structure, or the central nervous system. But most-mortem or post-conflict studies of shooting victims show that many 9mm, .40, .357 SIG, .45/.45 GAP, and 10mm self-defense rounds will do the job. The diameter of the round is important, but expanding bullet designs have done much to reduce the performance differences between calibers.
It has been argued elsewhere that larger diameter rounds that cause the target to "bleed out" more quickly are important, but I've also been led to believe that the primary job of a self-defense or home defense round is to hit something vital that STOPS THE ATTACK QUICKLY -- the person who wants to survive a self-defense conflict can't wait for the attacker to bleed out. (Even if you hit the attacker in the heart, he or she may still have almost a minute to hit you in the same place!)
Secondary wound cavities and energy transfer, once much talked about, now seem to be of less interest than was once the case, at least for handgun calibers. This is probably due, at least in part, to the fact that there are too many well-documented examples of aggressors continuing the attack despite many well-placed handgun hits to the torso. Secondary wound cavities (i.e., cavitation) seem to be disabling mostly with rifle round velocities. which are in excess of 2,000 fps. Bleeding out the target is important too, both in military conflicts and hunting, and wounding the target, including loss of blood, is important, and that happens most quickly with rifle rounds. Even the best handgun self-defense rounds seldom get close to rifle velocities (or distances.) As I noted earlier, if they an attacker has time to bleed out, he or she may have enough time to kill you.
That said, I'll now go away and continue to struggle with the physics (which I only poorly understand) and re-read parts of my sole reference book on ballistics (i.e., Understanding Ballistics - Basic to Advanced Ballistics Simplified Illustrated and Explained by Robert A. Rinker.) This text came highly recommended on several other forums, and if anyone knows of a better source, please share it with me and everyone else participating here.
