The November issue of American Rifleman [print only] contains an interesting article about expanding bullets. Although the article is aimed at hunters, there’s some insight for those of us who skew towards defensive firearms. Author John Barsness does a great job of breaking down the factors that constitute “stopping power”—though that phrase is never mentioned . . .
As our better informed readers know (i.e. all of you), the only way to instantly stop a 150-200+ pound threat is to either disrupt the central nervous system (CNS), or cause a sudden drop in blood pressure, aka shock. To that end, I bet that most of us who live in states that abide by the Constitution generally use +P hollow points in our carry guns.
[Don’t worry, the article isn’t one of those “broccoli causes cancer and bacon cures it” exposés. It’s just that placement matters much more than bullet performance.]
The three +1 measurable metrics that define bullet performance are energy, penetration in a standard medium, and expansion and weight retention. There are two contradictory theories regarding energy, expansion, and penetration.
On the one hand, someone might say that a bullet that didn’t exit the target did not penetrate enough. On the other hand, some would say that a bullet that exited the target did not impart all of its energy. While the intelligent observer might fall into one camp or the other, the truly sharp will realize that neither tells the whole story.
First, expansion and weight retention . . .
In the article, the author relates how he shot a prairie dog with a 180 grain handload out of a .30-40 Krag. The exit wound was ¾ of an inch, indicating that even in an animal that small, the bullet had time to expand. According to the author most hunting bullets will have fully expanded by the time they penetrate their own length.
I don’t know how true that is for defensive handgun rounds, but it is interesting. Furthermore, with very high velocity cartridges—think 5.56 and hotter—the goal is fragmentation rather than expansion and weight retention.
Although hunters typically only use these calibers on very small game, the US military seems to think it is suitable for use on people. Of course, neither people who shoot varmints nor the military are worried about damaging the meat.
Next up, energy . . .
Energy is easy enough to define; Newton did it for us four hundred years ago. But what does it mean in terms of stopping power? I honestly don’t know how energy affects performance. If a hot +P 9mm has roughly 450 foot-pounds of energy, what does it mean if the bullet did or did not exit the target? Assuming that the target stopped the bullet, then where did that 450 foot-pounds go and what did it do?
Most likely it just got converted into heat and then dissipated, which is how car brakes work. If someone could explain to me how dumping energy into the target disrupts the CNS or causes a loss of blood pressure I would appreciate it very much. The author and I agree on that point.
Saving the best for last, penetration . . .
Neither bad guys nor moose consist of a standard medium. They have bones of varying sizes and possibly clothing. Here again, placement is key; how far the bullet will penetrate depends on what it is penetrating.
The two elements of bullet design that affect penetration are weight retention, and expansion. The author’s wife shot a moose that was quartering away with a 150 grain Nosler partition and it penetrated 30” of the chest cavity through mostly soft organs. The same bullet had been stopped in less than 15” when fired at the shoulders of an elk, the difference being all the big muscles and bones in the way.
In the final anecdote of the article, a friend of the author shot a 100 lb deer with a 360 grain wildcat moving at 2700 fps. That’s over 5800 foot-pounds of energy. The bullet retained 90 percent of its weight, but expanded over twice its diameter—and did not exit the deer. The large frontal area was sufficient to slow it in the small target, a different bullet design probably would have gone through.
So what does it all mean? I’m more confused now than when I first read the article. I think I am sticking to my own theory: assuming that there is nothing important behind the target, two holes are better than one for reducing blood pressure.
Remember that little deer? The most important point in the whole article as far as defensive use of firearms is concerned: the deer was not even knocked down. It actually stumbled a few yards before it fell down and died.
Think about that. According to this author and others, after a hit to the chest cavity, it takes at least 10 seconds for blood pressure to drop enough for the target to stop moving. If a bad guy is coming at you with a weapon, especially a knife, those will be the longest 10 seconds of your life.