Home Forums Hunting & Shooting Ask The Gunwriters Minimum energy for Whitetails....

You'd certainly think so, and I did for a long time. It's not the case. Within normal limits, it actually works the other way around for penetration. Of course, there are two "levers" for adjusting kinetic energy, mass and speed. But if you're sticking with just one bullet type, speed is the key variable.

An expanding bullet that impacts at 1500 FPS will out penetrate the same bullet at 2500 FPS. That's because the slower bullet does not have enough speed to reliably open, and it just pencils on through. And the 2500 FPS bullet will out penetrate a common cup and core bullet at 3200 FPS.

Common cup and core bullets open reliably at 2100 FPS (impact speed...some open at 1800). From there to about 2800 FPS penetration is very constant, about 14-16" depending on the type of tissue. So anywhere in the range 2100-2800 FPS, the wound channel is the same. Adding more speed does not lengthen the wound channel.

Above about 2800, penetration drops off because the bullet opens too much, too fast. Smack a critter with your 7mm Mag using a regular bullet at 50 yards and you'll get a lot less penetration than you would with your 7x57.

Premium bullets change the game. Many of those open reliably at 1800 FPS, and hang together up to warp 9.4. But, by and large, the wound channels they produce are very close to the constant length, regardless of impact speed. So it doesn't matter whether the bullet hits at 1900 FPS or 3100 FPS, the wound channel is the same length. Within those limits, a faster bullet does not get you more killing power, it gets you a longer flatter trajectory and the ability to carry enough speed to a more distant target.

Going to a fatter bullet gets you a fatter wound channel. A big critter like a cape buffalo has a lot of blood, and you have to poke a bigger hole to get it to bleed fast. For North America, 1/2" or so seems to be big enough, or so I'm told.

The game is getting a fat enough wound channel that is long enough to transect a major vital organ that will bleed a lot, like the heart, a major artery, the liver, or the lungs. Fatter bullets make fatter holes. Adding more speed does not make longer holes, it makes shorter holes.

Haven't read all the posts, but P.O. Ackley wrote that 1,200 pounds /feet of energy is the minimum for deer and 1,500 for elk. Of course, this was before premium bullets were so common and it is the energy at the animal (not muzzle)

Oh yes, a solid hit in the vitals with a bullet of less energy is better than a miss-the-vitals with a 375 H&H!

djs,

If P.O. Ackley ever killed a big game animal, he sure didn't write about it much.

As I recall, the info about foot-pounds for various animals in his book (I have had a copy since 1972 or so) was written by an engineer who hadn't killed very many animals himself.

PO didn't hunt much from what I could tell. The reason I never paid much attention to what he wrote about cartridges.

Back when we used to drink a lot of likker at night in the camphouse I've sometimes killed 'em of a morning when I had hardley any energy at all.

Here I posted the information above and Game and Parks just changed over the weekend how much energy is needed to kill our elk and bighorns in Nebraska. Sigh.

Went from 2000 ft/lbs at 100 yards and 26 caliber or above to 1700 ft/lbs at 100 yards and 25 caliber and above.

250 Savage doesn't quite do it, but the 300 Savage is now on the list without hotrodding it. Yes!

Doesn't changes like this make you feel good about what the wildlife specialists know?

The exception to this, as you alluded to, is when using a bullet whose design stops expansion at a certain point, whereby added velocity does increase penetration. An example is the TSX.

You can't drive a TSX too fast

I believe that Mule Deer's comment and Denton's explanation of it say all that need to be said.

Well, exactly

Never used an X on anything but paper,but suspect Scott is right...

The biggest trouble with minimum energy figures is that they fail to take bullet structure into consideration.

Over on another website, there is a rather thorough series of tests done by an astute member,involving Raptor Bullets by Cutting Edge...it seems to demonstrate that the old rules regarding velocity and penetration are sort of "out the window",at least with those bullets.

I'm the best looking guy on the 'Fire

Equally true...

I edited my last to make your latest post more germane.

LMAO! We can always expect the unexpected from you Scott....

But who am I to argue?

The most modest also.....

I have killed Coues whitetails that weighed 90-120 lbs. on the hoof using a .270 with 130-grain NPs and a .280 AI with 140-grain NPs. I have also killed Kansas whitetails that weighed over 280 lbs. with a .222 Rem Mag (ballistically indistinguishable from a .223) and 52-grain Nosler SBs. All them were taken with one shot and none were lost.

We agonize way too much over minor details, but I guess that's what makes it entertaining for some of us.

I thought the minimun caliber for KS deer was .23 or larger?

Not if you have a scientific collecting permit. You get to shoot a lot more of them, too.