Big-Bore Ballistics: Are Muzzle Energy Calculations Useless Information?


The topic of terminal ballistics is normally addressed from the perspective of rifle ballistics. In his new book, Big-Bore Revolvers, Max Prasac looks at terminal ballistics from the perspective of the big-bore revolver, and dispenses some of the myths he says are frequently perpetuated by the hunting/gun magazine industry as a whole. According to Prasac, when conventional wisdom is repeated so often as to become law, rarely is that piece of wisdom challenged. Until now.

The fact that I am referring to energy as a myth flies in the face of conventional wisdom. After all, ammo boxes are stamped with energy figures, and ammunition retail websites offer ballistic comparisons between cartridges, with muzzle energy as the comparative figure. Gun magazine articles talk endlessly about the energy of hunting cartridges, and books about hunting are filled with references to energy as a determinant of effectiveness. Energy has been utilized to rate the lethality of cartridges/loads for some time now. But what is energy? Is it definable? Is it measurable?

This hole in the ribcage of a bull elk was produced by a 180-grain TSX from a .300 Win Mag. Impact velocity was estimated to be 2,600 fps at the range it was shot, which calculates out to approximately 2,700 ft-lbs of muzzle energy.

Ask any proponent of energy to define how it enables a bullet to kill game, and he will respond in vague terms. Really press him, and he will accuse you of having a poor understanding of terminal ballistics. Yet, even many game laws call for muzzle energy minimums for specified game. Seems like everyone is in on the sham! The terms “energy,” “energy dump,” “kinetic energy,” “muzzle energy,” et al, are tossed around with utter, complete, and unfounded confidence by their proponents—until forced to explain.

A number of African big-game hunters I have been in contact with and who have killed numerous elephants in their days often cite that a minimum safe (effective) cartridge for hunting elephant must have a 400-grain bullet and 5,000 ft-lbs of muzzle energy. I have not killed an elephant with a revolver (nor with a rifle), so I defer to those with this experience. Now, in their significant experience hunting elephant, their summations have held true, as most of the cartridges utilized on elephant have met this minimum requirement. And, in the cases where they have not met this arbitrary minimum, it has been noted that the cartridges in question have not worked very well.

This hole, same bull elk, and also an exit hole in the ribcage, was produced by a 440-grain wide, flat-nosed hardcast bullet in .500 JRH, loaded by Buffalo Bore at an advertised 950 fps at the muzzle. The muzzle energy is calculated to be approximately 888 ft-lbs. Muzzle energy, as a determinant of lethality, is an exercise in futility.

So, having said that, what if I shoot an elephant with a frontal brain shot with a revolver in .475 Linebaugh loaded with a 420-grain bullet at 1,300 fps, and I have enough penetration to reach the brain and dispatch the elephant? Clearly, this load does not meet my colleagues’ minimum requirement in one of the two criteria. Yet, surely my cartridge is adequate despite the “inadequate” muzzle energy. By the way, a 420-grain bullet at 1,300 fps “generates,” or rather calculates out to, a whopping 1,576 ft-lbs. Supposedly it’s not enough, even though it kills the animal door mouse dead.

Energy, as such, can not be measured. Muzzle energy figures are calculated. Fortunately, once the energies are calculated, you can file them away in the useless information bin. Yup, muzzle energy has no reflection on the lethality of one round over another. Any .22-250 rifle round loaded to spec will create a higher muzzle energy number than some loads for the .454 Casull. Which one would you rather have when facing down an angry grizzly bear? For me, it sure wouldn’t be the .22-caliber round, despite its energy “advantage.”

To read more, get your copy of Big-Bore Revolvers today. There is something here for the beginner, the expert, the weekend warrior, and both the mildly and keenly interested. Topics include:

  • Cartridges
  • Platforms
  • Custom guns
  • Care and feeding of your big-bore revolver
  • Bullet types, energy, and other myths exposed
  • Sighting systems
  • Holsters
  • Shooting your big-bore revolver
  • Pioneers
  • Tales from the field: Hunting with a big-bore revolver

So sit back, savor the smell of smokeless powder, and enjoy the ride.

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  1. Cymond says:
    >If muzzle energy is such a bad metric, then what do
    >you propose? Velocity? Bullet diameter? Bullet
    >weight? Bullet design? Any one factor, without
    >the others, leads to obvious nonsense.

    Yes–all of the above!

    As long as we must calculate “knockdown power,” I like the WAVE formula discussed in the Mel Tappan classic, “Survival Guns.”

    W x A x V x E

    weight (more correctly, mass) x caliber cross sectional area x velocity x bullet efficiency

    Bullet efficiency is 1.0 for a non-expanding bullet like FMJ and as high as 1.25 for a good expanding bullet.

    Note that this metric is proportional to the square of the caliber (pi x radius ^2) This seems to be a better predictor of killing power than energy, which is proportional to the square of the bullet speed (velocity).

    There are other similar formulas but WAVE is easy to remember.

  2. As Peterson shows above, energy alone is a poor indication of effectiveness. However, it is the best way to compare similar loads. How do we choose between a .30cal 110grn bullet at 2700 fps and a .30cal 124grn bullet at 2400 fps?

    If muzzle energy is such a bad metric, then what do you propose? Velocity? Bullet diameter? Bullet weight? Bullet design? Any one factor, without the others, leads to obvious nonsense.

    It’s a well known fact that .223 Rem is widely used for coyotes. Would anyone recommend 22lr for that role? It’s the same caliber and weight as .223; only its energy/velocity is different. Deer are taken with .357 Rem Mag, but would anyone recommend .38 spcl target loads for the same role? I mean, they fire the exact same bullet, so they should be equally capable, right? The only difference is their velocity and their energy as it relates to velocity. Caliber and weight alone are not enough.

    Is a bigger bullet better? Generally yes, but it’s a little complicated. Increasing bullet size without increasing weight means a large round-nose bullet with a poor ballistic coefficient and poor penetration in the target. Maintaining sufficient penetration requires either increasing velocity (same weight) or increasing weight (same velocity). Either solution means increased muzzle energy (and recoil).

    Characteristics of a perfect cartridge:
    a large caliber to damage as much tissue as possible
    a heavy bullet for deep penetration
    a high ballistic coefficient for long range
    a high velocity for range and penetration

    A cartridge like .50 BMG would satisfy all of those requirements, but it’s not exactly practical to drag through the field.

    Is energy everything? No, it doesn’t account for everything but at least it considers multiple factors. That’s better than simply looking at a single factor. If someone has a better metric, please provide it.

    • Great discussion points Cymond – Thank you for taking the time to post the comment. It seems to me that the ‘perfect cartridge’ depends heavily on what it is you plan to do with it. And, as you noted, relying on any one of the factors, without considering the others, may not be the best way to choose an effective load for your purposes. Someone who understands the factors noted in your comment, and in Prasac’s book, will be better able to choose the best ammunition for their needs.
      Thanks again for posting, and for reading the Books blog!


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