This is not part of the main story; it's a science popularization chapter!

(Some readers have said that the main text’s explanations of hard military knowledge are too verbose, accusing me of padding for length. That’s truly disheartening, so I’ll list such sections separately from now on. In the future, I will continue this practice. Readers who enjoy this can click and learn a bit of military knowledge—never be a complete novice again! Those who don’t care for it can simply skip ahead; it won’t affect your reading experience.)

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A bullet’s wounding characteristics are numerous, but the damage it inflicts on humans is generally categorized into two kinds: penetration (or through-force) and stopping power (or incapacitation).

A bullet with strong penetration may simply punch a hole straight through, but its terminal effect is sometimes surprisingly minimal. Take, for example, the Type 38 rifle used by the Japanese during World War II. Its ammunition was full-powered, with long range, high velocity, and formidable penetration. A single shot would pass cleanly through a person, and the bullet would continue flying without losing momentum—a neat, almost surgical wound. There would be just a small entry and exit wound, the bullet wouldn’t tumble or create a cavity, nor would it tear out a chunk of flesh as it exited. The entire process was smooth—almost too clean—and thus the destructive power was not as high as one might expect.

In some books, movies, and TV dramas, it’s depicted that many of our resistance fighters were shot several times, yet unless the bullet struck the head or heart, they could still battle heroically for a long time. Many viewers joked that these were “superhuman dramas.” In truth, this is not an exaggeration: after being shot, one really could keep fighting for quite a while. The problem was that the Type 38’s penetration was so great that, despite its overwhelming power, all it left was a neat little hole. Bleeding to death actually takes quite some time.

It’s like the familiar “pulling the paper from under a bottle” trick: if you pull fast enough and with enough force, the bottle on top barely moves. The process is so smooth that the surrounding objects aren’t affected at all. But if you pull slowly, or use a piece of coarse cloth with higher friction, the bottle is dragged along and tipped over. Comparing the paper to the bullet and the bottle to the human body, that’s the difference between a bullet that takes a chunk of flesh out and one that just passes through.

Of course, when penetration is necessary, the stronger the better—adequate armor-piercing capability is a must on the battlefield. The Type 38 simply failed to account for the fact that the human body isn’t “hard” enough. In its pursuit of long range and high penetration, its designers inadvertently reduced its lethality against people.

So, how can a bullet’s destructive power be increased to the point that one shot can bring down an enemy? That’s where “stopping power” comes in.

Stopping power refers to a bullet’s ability to incapacitate the target upon impact. The greater the stopping power, the faster the target loses the ability to act; the lesser the stopping power, the longer the target can keep moving. Given the same powder charge and bullet weight, lengthening the bullet and sharpening the tip yields greater penetration and higher velocity—traits characteristic of armor-piercing rounds.

(A “grain” is a standard unit of bullet weight, roughly equivalent to a single barley corn.)

Conversely, bullets designed with blunt tips, hollow points, or expanding features, or those made heavier and shorter, all serve to increase stopping power. The Soviets, for example, abandoned mature full-powered rounds and developed an intermediate cartridge specifically for the legendary AK-47, all in pursuit of greater stopping power.

Consider the difference between a needle and a hammer: a needle’s penetration is superior, but no matter how hard you jab, it only makes a small hole; a hammer, with its inferior penetration, can shatter bones in one blow. In human terms, bullets with large calibers, blunt or hollow tips, and excessive mass lack aerodynamic points and thus don’t penetrate smoothly, but they carry immense kinetic energy.

When such a bullet hits the body, its lack of penetration means it can’t glide cleanly through and out the other side. Instead, propelled by brute force, it tears open the skin and burrows in. Once inside, these stopping-power rounds—with no streamlined shape—lose balance upon contact with muscle and begin to tumble. Fueled by their kinetic energy, this tumbling is catastrophic. The bullet, already spinning from the rifling, loses balance and spins erratically, doubling the centrifugal force and creating a horrifying cavity effect.

The flesh around the bullet is torn apart; as the bullet exits, it drags out a large chunk of flesh and skin. A wound the size of a peanut going in, but a crater the size of a bowl coming out—this is the terminal effect of stopping power: the deadly cavity created by tumbling and spinning.

And if the bullet doesn’t exit the body, the internal devastation is even more horrific. The bullet, gleefully spinning, acts like a crazed, headless fly, careening through the body and wreaking havoc on internal organs. There are accounts of a bullet entering through the buttocks and exiting at the shoulder, but such extreme “turning” cases are rare; even if the bullet eventually emerges, the body inside is already shredded beyond repair.

The tearing wounds caused by stopping power swiftly rob a person of any ability to move—most likely killing them on the spot.

Yet, in our current era, where body armor and ballistic plates are standard issue for every soldier, the need for one-shot incapacitation is no longer a military priority; it’s more relevant for police firearms. Military long guns may seem more formidable, but often their wounds to the human body are, paradoxically, less cruel. In contrast, law enforcement sidearms, which may appear unimpressive, are designed to maximize stopping power—one shot to end resistance—making their wounds far more devastating.

For instance, after the American army switched to the 9mm M9 pistol, the retired .45 caliber M1911 remained immensely popular among police. Similarly, large-caliber revolvers—frequently seen in Hollywood blockbusters—are also beloved by law enforcement.