It’s true that some bullets expand less violently than others. This can create the impression that they’re opening more slowly, but the difference lies in how much the bullet fragments upon expanding. The clearest example of this is the “varmint” bullet that disintegrates in order to kill small pests instantaneously. At the other extreme is a heavy-duty, big-game bullet designed to retain most of its weight. The first creates a huge hole immediately upon impact. The second makes a smaller hole upon impact, then continues onward, creating a narrow, long “wound channel.”
Big-game bullets often punch through the hide on the far side, sometimes leaving an exit hole not much bigger than the entrance hole. Many hunters take this small exit hole as evidence that the bullet didn’t expand at all—which makes me wonder if they actually field-dress the animals they shoot, since damage inside the chest makes it obvious the bullet expanded.
I first became suspicious about the “slow-expanding” bullet theory about a decade ago when using a High Wall single-shot rifle in .30-40 Krag to shoot prairie dogs. I’d planned to hunt deer with that rifle, using a tang-mounted rear aperture and gold bead front sight, so I took it prairie dogging with some 180-grain Winchester Power-Point handloads. My companions found this amusing until just before noon when a prairie dog stood up around 200 yards away. I held the top of the bead on the varmint and shot. It tipped over, and when we investigated we found a small hole in its chest where the bullet had entered—and a 3/4-inch hole in its back, where the expanded bullet had exited. The reason the animal didn’t come apart like those shot with .22-.250 Rems. is that the tougher bullet from the .30-40 didn’t disintegrateᰬbut it still expanded, and obviously quickly.
There’s one exception to this bullet behavior, the Berger Very Low Drag (VLD) bullet. Several years ago a few hunters started using these thin-jacket, soft-core “target” bullets to hunt deer and other big game. The VLDs did not disintegrate immediately upon striking animals, but inside them. In fact their entrance hole looked like it was poked by a knitting needle. How could this be?
Hunting bullets expand because their front end is weakened. Sometimes this is accomplished with a hole in the front end (making a “hollow-point”) and sometimes by leaving the lead core exposed (“soft-point”). Both can be further weakened by longitudinal cuts. The front end collapses outward (“mushrooms”) when the bullet strikes an animal.
In theory a hollow-point bullet opens when the cavity is forced wider by fluid or flesh. I am not so sure about this, because my favorite “tough” bullet test is a stack of dry newspapers. Even relatively hard hollow-points like Barnes X-Bullets will open up in fluid-free newspaper.
Also, I’ve tried poking the tip of a small safety pin into the hollow-point of a 168-grain 7 mm VLD and the pin simply stopped. In effect there is no hole in the tip of a VLD. The jacket, however, is extremely thin, and the tip of the bullet extends beyond the lead core, so the tip itself is hollow. Apparently the long, sharp ogive allows a VLD to pierce the hide, plus an inch or two of tissue beyond it, before the thin jacket collapses and the bullet upsets violently. This has since been demonstrated thousands of times not only in test media but game animals. In fact it normally works even when the bullet impacts light bone. The Berger VLD is among the quickest-killing deer bullets around because it disintegrates inside an animal, opening more slowly than standard big-game bullets.
The odd thing is that Berger recently introduced a heavier-jacket version, though not for hunting. In some target rifles the original, thin-jacketed version didn’t hold up, especially when shot from cut-rifled barrels. So the thick-jacket version of the VLD is the “target” bullet, and the thin-jacket VLD the “hunting” bullet. Obviously this goes against the “rules” of big-game bullet behavior that every hunter knows.
This isn’t because the hunter in question has actually studied the subject, but because he heard stuff ’round the campfire or read it in magazines. Among other things, he’s been told that “shock” is a major factor in how expanding bullets work. When asked to explain shock the hunter in question often becomes irate, and responds with, “Everybody knows what shock is!” Maybe, maybe not. Let’s look up shock in an unabridged descendant of Noah Webster’s dictionary. It turns out there are a bunch of shocks, including sheaves of grain, the physiological effect of an electric current and being startled, as in “the rebuke came as a shock.” Obviously those don’t apply, since hunters don’t zap deer with 110 AC, slap them with a wheat-whip, or rebuke them into the freezer. The definitions that could apply are: