Bullets Too Fast to Expand?

Can you shoot bullets too fast to expand when they strike game?

Some folks seem to think so.

Bullets Too Fast for Bears

I was in bear camp where our Canadian guide, a capital fellow, was doing his best to make sure his clients were properly prepared for their hunts. He drove us all to a shooting range with solid benches for zeroing. “What are you shooting,” he asked each of us. A 300 Winchester Magnum. Good. A 300 Weatherby Magnum — even better. A 338 Win. Mag. Excellent. A 30-06. Proven beyond a doubt.

“I brought a 7mm Rem Mag,” I said, holding forth a Borden Timberline topped with a 3.5-18x44 Swarovski Z5.

Uh oh! Houston, we have a problem…

Jim Borden’s bolt-actions and Timberline rifles are widely respected around the country. Jim has used them to win numerous precision shooting competitions. But the rifle wasn’t the problem. It seemed our host didn’t think much of Remington’s famous 7mm magnum. “It shoots bullets too fast,” he said when I asked what the problem was. “Bullet doesn’t have time to open.”

He was not the first to voice this complaint. I’ve heard it several times over the 50 years I’ve been plumbing the depths of our fascinating hunting rifle world. When I first heard it, I took pause. But then I pondered. And then I investigated. Could the 7mm Rem. Mag. — or any other high velocity cartridge — really spit bullets too fast for their own good?

"Bullets Too Fast" is a Historic Argument

To contemplate this question, I first had to lay aside the Keith vs. O’Connor 270 Winchester acrimony and all the anti-Weatherby hyperbole I’d been hearing since the 1960s. I wanted to concentrate on physics to figure out if we can we really shoot bullets too fast to expand.

The first thing I asked myself was “how fast is fast?” The 7mm Rem. Mag., for all its fearsome reputation for hypervelocity, pushes a 150-grain bullet only about 3,100 fps. The beloved and highly respected (justifiably) 300 Win. Mag. shoves a 150-grain bullet about 3,260 fps. So how can the 7mm Rem. Mag. be too fast if the 300 is considered a knockout champ? Clearly something else is going on.

At What Ranges are Bullets Too Fast?

The second thing I asked was how "far" is fast?” Muzzle velocity is one thing, but we all know bullet velocity is a lot like us. With time it slows down. At 300 yards the 7mm Rem. Mag. bullet is going slightly slower than the same bullet shot from a 7mm-08 Remington at 100 yards. I’ve never heard anyone complain the 7mm-08 was too fast for its own good -- at any distance. And I've never heard the "bullets too fast" theory limited to close shots. If someone complained about cartridges exercising excessive speed, it counted at 200, 300 and 400 yards, too.  

The third thing I asked myself was what causes a bullet to expand? Best I can figure, it’s three things. 1. Impact energy. (A direct product of velocity.) 2. Target medium. (A sheet of paper ain’t the same as a side of moose.) 3. Material and construction of the bullet itself (A solid isn’t going to respond like a hollow point.)

A "Bullets Too Fast" Thought Experiment

Let’s consider these things against a small thought experiment: Perch a bullet, nose up, on a steel anvil and drop a 16-ounce framing hammer on its tip from 12-inches overhead. Voila! Expansion. Now do the same (fresh bullet) with the hammer dropped from 24-inches, then again from 36 inches. It’s pretty obvious which will flatten the bullet more. The hammer mass remains the same, but the velocity increases, thus more force and more expansion.

This may not be an accurate comparison to bullets striking game, but it sounds right to me. The faster the hammer (bullet) moves, the more energy it carries, thus the more it expands on impact. Not only is kinetic energy highest at top velocity, but it's highest the instant the bullet makes contact. That’s its maximum force. How can it not initiate immediate expansion? Deeper into the target medium it will have slowed, it’s energy will be less and so will expansion, no? It’s not as if the bullet has some sort of internal mechanism that cranks it open, thus requiring enough time in the target to accommodate that opening. It’s merely the combination of impact energy and friction that does the job, and the faster the impact velocity, the higher the energy. Sure, it takes a split second for the bullet to fully mushroom, but that’s more a product of bullet construction than speed.

During its passage through an animal, a bullet is constantly losing energy, steadily losing the forces needed to make it expand. I just can't picture how more time at an ever decreasing energy level can help. After all, consider what happens when a 55-grain hollow point from a 220 Swift hits a prairie dog at 3,300 fps. Not a lot of time needed there!

Photo of bullet fired into wax tubes shows that bullets too fast to expand is a myth. All expanded full after one to four inches of travel.

My eyes were opened to the rapidity of bullet expansion many years ago when I watched a super-slow-motion video of a Barnes X bullet penetrating an apple. Barnes copper bullets are widely known for being extremely tough, even to the point of sometimes failing to open. Yet this one emerged from the demolished apple fully expanded. Search the Internet for "bullet expansion in gel videos" and you'll see lots of slow motion footage of various projectiles hitting ballistic gelatin blocks and expanding. Note that they all begin expanding immediately and fully expand within an inch or three of impact. At that point wound channel diameter is maximum. After that they merely bore forward at decreasing speed.

So my conclusion is that all of these decades of “too much bullet speed” arguments should really have been bullet construction arguments. Which bullets should you use with a high velocity cartridge vs. low? And while you’re deciding that, don’t forget distance. At 300 yards a 168-grain boat tail spire point from a 300 Win. Mag. is carrying about 180 fewer foot-pounds of energy than a 170-grain 30-30 round nose at 100 yards.

How My "Bullets Too Fast" 7mm Rem. Mag. Borden Rifle Performed

Meanwhile, back in that Canada bear camp, I went hunting with my too-fast 7mm Rem. Mag. Borden Timberline, flung a 150-grain Barnes TTSX at a big, old boar -- and broke out the skinning knife.

Can you shoot a bullet too fast to expand? Not if it’s the right bullet.

After 50 years of hunting, Ron Spomer, like any good hunting bullet, has been slowing down. He offsets this by continuing to hunt with rifles and cartridges that launch bullets really fast.