We do know a lot about terminal performance from hunting, not just self defense. Heavier bullets for caliber and better sectional density lead to superior penetration, as far as weight is concerned with bullets, when isolated from other aspects, we more than understand the importance of this. When bullet design stays the same, heavier weight bullets are chosen for penetration, this is age old. Weight and sectional density matter a lot, and you can't simply sweep it under the carpet.
The 115 grain hollow point bullet was based on an extremely flawed theory in the 1970's and early 80's based on the theory that temporary cavities from bullet shock caused damage, and lead to stoppages in attacks. This lead to the flawed idea that maximizing temporary cavity and shock was the means to increasing effectiveness of handgun rounds, and an entire science was formed around this, using 20% ballistics gel and measurements of temporary cavities in these gels. Since fast, light bullets for caliber caused the greatest amount of shock in these tests, all of the experts at the time said that light and fast bullets were now super duper awesome cutting edge super one hit stopping ultra mega bullets. The experts took the flawed conclusions of the metrics and immediately went to the pulpit in front of LEO's and preached from the mighty gospel of fast handgun bullets. With great firebrand preachers for the new cult, they converted many a heretic to the One Truth of handgun terminal performance, that speed and shock are everything. Did you know that the Glaser Safety Slug is the best bullet ever designed?
Low and behold, true believers, it turns out the theory and conclusions they drew were absolutely wrong. The great new cult was built around misunderstandings and bad scientific conclusions, a deeply flawed theory. It turns out that almost no handgun can produce hydrostatic shock, and that temporary cavities are of little to no importance in stopping attacks. The 20% gel tests also purposely exaggerated these effects, making the illusion worse. It turned out the primary, and perhaps only, mechanism of stoppage was the actual crush cavity from the bullet itself. The super duper ultra mega super one hit man stoppers turned out to not be what they were said to be by the preachers of the new terminal ballistics cult, but the myth lives on today through those who still believe.
No matter how well you design a bullet, weight and sectional density will limit its potential. That's a dead on fact. Handgun bullets are already light for caliber to begin with, and sectional density is always an issue. All standard handguns area also low velocity and low energy. 1150 fps, or 1350 fps may be relatively fast for a handgun, but its still very slow. You don't really hit high velocity till you break the 2000 fps mark, and no "high velocity" handgun does that, much less a 115 grain 9mm Luger. No, the velocity is not high enough to create effective shock in tissue, no, the energy isn't high enough either. Its a medium power handgun, a low power cartridge, and a low velocity projectile.
So, when we talk about handgun bullets, and expanding bullets, what is best? Handgun bullets don't penetrate very well to begin with, weight, velocity, energy, and sectional density all considered, they aren't spectacular to begin with. The supposedly dangerous FMJ over penetrating tissues has been greatly over exaggerated, and non expanding bullets often times don't go through targets. If a non expanding bullet can fail to punch through a man, what does that say about expanding bullets? The answer is that we should be careful that the bullets don't fail to punch deep enough because of the increased surface area and resultant drag reducing penetration, not to mention bullets absorb their own energy in expanding. They can easily fail to get deep enough in angle shots.
So, if we need to make sure we can punch deep enough with our expanded bullet, what's the best way to go about it? One way is to build a better bullet that won't fragment or over expand. This is key to success, and preventing failure. The other is giving it the advantage of weight and sectional density, increasing its ability to penetrate deep even with the increased drag of crushing a bigger cavity with its bigger expanded face. It would appear for the handgun, with its limitations, would be best suited to use the heaviest bullets for caliber available when using expanding bullets. Using a higher velocity, lighter bullet simply doesn't seem to make sense, and in fact, fliess in the face of what we know about terminal ballistics.
Yes, you can attempt to design a bullet that will expand less and mitigate the problems of the light bullet, but that won't change the end limitations. Sure, they can and have designed 115's that won't fragment or they control expansion to prevent it from under penetration, but in truth, these bullets still under perform against heavier rivals. In the end, design can't make up for real physics and real physical limitations.
The people who believe in the Cult of the light bullet will often times pull out the old flawed science or Marshall and Sannow's work to prove they are right. Prove to them the old tests were flawed and the books they read are poor statistical hack work, they tend to degrade into "terminal ballistics don't matter, shot placement is everything" and generally try to change the subject to something other than the subject at hand. The same people who bash modern ballistics gel testing are sometimes the same people who preached to you about the old gelatin tests being final proof of smaller calibers and lighter bullets being superior. They ignore the science when its convenient.
Lastly, the 125 grain .357 Magnum rounds did well. But, what about the 158 grain hollow points? Just because .357 magnum had the power to make the 125 work well, is there the possibility that there is better? Could it be a hotload 158 grain hollow point of the same build might actually out perform the all sacred 125? Could it be, that even though the 125 grains were incredibly effective, that perhaps there was something even better? The 125 grain bullet argument always seems to state that 125 worked in 357, but I've never heard of any of these people ever mention if it was better or stacked up against other .357 Magnum rounds. They state the 125's grand superiority as if it were the best, without ever once stacking it up against alternatives.
