View Full Version : Killing Power! (some interesting reading)

01-24-2011, 02:35 AM
Something I found a while ago I thought some of you folks here might find interesting. I thought it especially suited, considering cast bullets can lean more towards the "slow and heavy" side of things. I figured it fits as well here as anywhere else.


"A study in bullet impact". Killing Power, or Kinetic Pulse, or just plain KP. Basically, this guy (James N. Hall) formulates a way to consider both kinetic energy and momentum in the analysis of a bullet's terminal performance. It's a bit of a long read, so I'll try to give a basic idea of it here:

The volume of a cavity created by a projectile when it impacts something (clay, for instance, or a body) is proportional to its kinetic energy multiplied by its momentum. The KP is given in terms of the volume. The more kinetic energy something has, the more "splash" it has; and the more momentum something has, the deeper it tends to penetrate. So you can view the displaced volume as a cylinder, with the kinetic energy representing its circular cross-section, and the momentum representing the "depth" or "tallness" of the cylinder. You can then keep those dimensional proportions in consideration when assessing KP for different targets (thick vs. thin).

That's a very basic idea. He has lots of math on it, did stuff with units I don't mention here, etc. Lots more is said. One thing he doesn't do is consider different diameters/shapes of projectiles - not because he forgot, I am sure, but probably because he hadn't found a way to represent it. He says that the projectiles compared with this method are presumed to be identical (except in mass). He gives lots of examples and data for a large variety of cartridges.

Overall, if you're at all interested, I suggest you read it. I give a rather shoddy portrayal here. There are also links at the bottom of the page which are interesting (a KP calculator among them).

I don't think this is the ultimate word on anything, but it's interesting, and I think it is worth having in mind. Hope you enjoy! :-D

01-24-2011, 04:14 AM
Very interesting, but Lawdy! I wish he would have used a white background!

Old Goat Keeper
01-24-2011, 04:54 AM
Looks like this guy came up with reasons why: 1) why you can eat up to the hole with a big slow bullet, 2) why a high speed bullet makes a lot of blood shot meat and 3) why some caliber/bullet weight combinations "seems" to kill so much better than you'd expect.


01-24-2011, 01:53 PM
One of the things I think these math gurus miss is that fact that energy at high velocities also act on the bullets, probably more so than the game. Consider that my 32 long with a wadcutter will cut a nice clean hole in a paper taarget that looks better that what my 300 Savage will cut. The paper does not absorb much energy. Nosler developed his bullets, some say. because he had problems with his 300 mag on dangerous game. The standard bullets were breaking up too much due to the energy of the 300. If one reads about the headaches they have had making solids for African game wou will see the same effect. A while back a very experience writer mentioned that bullets seemed to behave the best when driven at under 2900 fps and even 2700. I ahe been so impressed by the performance of cast bullets at about 2000 or less that I do not like jacketed bullets. Teh cast bullets stay together, blow big holes, leave good blood trails and the deer go no farther than with jacketed. High velocity was designed to deliver a killing effect at longer ranges, when used up close it can cause problems. The two great calibers by those that had to shoot a lot of African game are the 9.3 by 62 and the 375 H & H. None great shakes at velocities but excellent performers.


01-24-2011, 04:54 PM
One should also read the writings of Homer S. Powley about killing power.
Twice as heavy, half as fast=more killing power.

01-24-2011, 05:19 PM
I'm glad to see I seem to have made an appreciated suggestion.

And thanks for pointing us towards Homer S. Powley, oneokie. I'm off to find something by him right now! :mrgreen:

01-28-2011, 09:35 PM
I agree with waksupi.

Yellow print on a purple background makes my eyes hurt.

Uncle R.
01-28-2011, 11:18 PM
I doubt that we'll ever see the end of one formula or another designed to predict or explain killing power. They all seem to be designed to give results that match the author's existing beliefs. Some believe that velocity is more important - some sectional density. Some place their faith in momentum - some in energy. You can come up with a formula to match your prejudices but the real question is does it match results in the real world. In searching for that answer there's no substitute for experience but even well experienced persons will often have wide differences in opinion.
Can you say Keith VS. O'Connor?
Uncle R.

01-30-2011, 12:07 AM
Punch a hole in something REALLY important and they fall down NOW. Less important,
it takes a bit longer.


01-30-2011, 12:28 AM
Here is a link to the 1904 military study.


02-09-2011, 02:57 PM
if it can be hunted and has been with a muzzleloader shooting a round ball then i feel comfy with my settup.

02-09-2011, 09:03 PM
Most formulas are trying to apply physics to biology. More than once I ahve seen a "Dear Abby, I live by posted land and need something to anchor my deer so that they do not go on to the posted land". Most will recommend large calibers "that really put them down". After about 40 years of deer hunting and seeing a lot of deer shot my recommendation is to use an adequate caliber and break their sholders. Don't much matter if you use a hard cast 44 and break their shoulders or a 30-30 load. You can even blow them up with a faster cartridge like a 30-06 or heck even a 300 super mag. But to consistantly anchor them you need to break them down. A friend of my sons has a blurb on you tube about shooting a deer with a 50 cal machine gun round. His brother made a soft point for it and the deer was hit behind the shoulders and ran about 70 yards with little left on the off side rib cage. Most of the big bore folks kind of want to ignore that little lesson and think their super mag will really knock them down. I shot a jack rabbit with a varmit bullet in a 222 that ran 80 steps before it keeled over. No rib cage on the exit and you would not think a rabbit had that much blood in him. It was in the snow so I could pace of the the distance from hit to rabbit. We ahve ben conditoned to aim behind the shoulder to save meat and it does. But you really have to stop the central nervous system or break the skeleton down to drop them consistantly.


02-10-2011, 03:40 PM
+1, northmn. Break em down. I shoot pigs exclusively through both shoulders if I can. This last season, I shot a deer at 75 yards with the Ranch Dog 300 gr. in 44 mag behind the shoulders. He ran some, fell and died. Shot another through the shoulders and other than being knocked flat, he didn't move. If you want em to stay, you gotta break em down.

02-11-2011, 06:30 AM
Good morning
All the reading is good for wet or cold days...
But when it all comes down to me I think I will stay with proven performance. One fat heavy soft cast boolit passing through a chest cavity is going to put an end to my hunger needs.

02-18-2011, 12:30 AM
I'm wanting to know how my boolits are going to perform, not which caliber I should be using (too late for that - I already have my guns). I'm thinking my boolits have two requirements, one is to reach the vitals from a disadvantageous angle and the other is to kill the beast from a favourable angle. That could mean putting a boolit into the chest via the head, neck and shoulder or from behind the ribcage forward. So far, the boolit has been tested on turkey and it killed them on the spot. Now to find a pig! The boolit is a 214gr 303 with a wide shallow hollow nose at probably 1600 fps. I'm thinking smashing those shoulders is good advice!

http://i388.photobucket.com/albums/oo327/303Guy/HollowNoseDesign.jpg It gets paper patched.

02-18-2011, 06:00 AM
I agree with waksupi.

Yellow print on a purple background makes my eyes hurt.

Much easier to copy and paste to MSWord to adjust the color choices. :bigsmyl2:

02-18-2011, 08:23 PM
Very interesting, but Lawdy! I wish he would have used a white background!

Here is a solution for black text on a white background (that will work for Microsoft OS).

Open the page in the link
Hold down the ctrl key and press A (select all)
Hold down the ctrl key and press c (copy)
Open Microsoft Word or Wordpad.
Hold down the control key and press v (paste)

The document will now be displayed with a white background.

03-12-2011, 11:06 AM
Over 30 tyears, I've pobably read most discussions on "Killing power", from most noteable writers and casters, some from field experience and some were downright blowhards with bullets named after 'em.
The technical discussions regarding metals and behaviours under heat, pressure and velocity is all interesting, but after a few years they all start sounding about the same.
Consider this : slap factor and penetration.
Bullet Weight x velocity at 50 yards x meplat diameter + a little common sense= Slap factor
Slap factor is nothing more than a simplistic number of what's gonna be felt on the receiving end. As practical as it is, this approach works well within similar calibers, but the factor falls apart comparing extreme examples...
Having said that, a pointy .22 FMJ at screaming hyper velocity just ain't gonna have the real world slap and slam of a 500 grain soupcan at 1400fps... that's where the common sense element comes into play.
At normally moderate ranges, Big Boolits and big meplats win, especially within a given caliber

03-12-2011, 12:39 PM
A number of years ago, I read someplace (maybe an early Gun Digest???), an article on this subject. One of the things that somebody came up with was: A volkswagon bug at I think 5 mph had more energy than a 500 gr blt. from a 458Win. Think it also had a mathmatical formula to prove that with the weight of the VW, speed, etc. Don't think it compaired the meplat of the blt to the bumper of the VW however. It was to me such a foolish comlparison of things at the time that it has stuck in my mind ever since.

I have never had a shoulder shot animal do anything but fall down, most often times dead by the time I got to it. Regardless, I did not have to track. To me that is a big factor, and not breaking down the animal is one reason for game being lost. Then there is the other side of the excuse that I have heard regaiding lost game---"The coyotes gotta eat also!" mentality.

I watch a fair number of the shows on the outdoor channel, and pay attention to shot placement and results. Shoulder shots anchor most anything, heart/lung shots seldom anchor, and result is tracking. Tracking may not be long, (if you are lucky) maybe as little as 100 yds, but often may be 5-10 times that far. If it is open country that may not be a problem. Dark timber more of a problem, swampy land, even more of a problem, etc.etc.etc.

Another factor to me is size of target, and a shoulder shot presents a larger target than a heart lung shot. Lots of emphasis on getting shots into the vitals, and I contend that a solid shoulder shot will in many/most cases be a vital shot depending on the angle of the shot.

And yes, you are going to lose a little meat. Big deal, better than loosing a whole animal. And if you consider the butchering skills of a lot of hunters, there will be a fair percentage of waste due to the lack of skill in that regard.

And a big thing today is premium blts that hold together and cost an arm and two legs. And yes they work and work well. However the heavy blunt cast blts of times past worked just as well. They worked just as well, maybe even better but at closer ranges. The long range deal on big game just doesn't fascinate me today like it did in the past. Think it was Taylor who advocated on elephant that you should get as close as you can, then get 5 yards closer before you shoot.

Had never heard of this " slap " factor, but kind of like the mathmatics of it, particularly the "little common sense". A comodity quite often lacking when it comes to this subject. The older I get the more I have become a believer that big, flat nose, moderate vol, and moderate range will bring home the bacon or venison.

Dixie Slugs
03-20-2011, 11:42 AM
Interesting indeed! Those that have read my posts over the years know that I stated years ago the following:
(1) Tissiue Damage is a product of Velocity and Meplat Area
(2) Penetration is a product of Sectional Density and Velocity.
Years ago I posted a formula to test the potential of one bullet design and it is as follows:
Sectional Density X Velocity X Meplat Area = Gates Force Factor
Now...the water in tissue creates Tissue Damage due to the fact it can not be compressed. The water in Tissue will be converted to a blood mist in a certain pressue is forced on it.
We have tried over the years to nail down some formula other that the nonsense KE.......which was based on a vertical steam piston!
There is a balance Sectional Density - Velocity - meplat Area that comes from Gut-Pile-Analysis.
In one post here on Cast Boolits, I discuss Extreme Meplat bullets for handguns. These bullets were designed to create massive tissue damage within reasonale hand gun ranges.
Regards, James