Cartridge suitability

[McCall911]

The big question which seems to be unanswered is which metallic cartridge is suitable for which type of game. I have always thought that this was worthy of an answer, but so far nobody has had a really good one. But some people, especially and notoriously gun-rag writers, have always been more than happy to try to sell me on some guns or ammunition that I might not need!

I've long had a little formula for my own personal use but I put it on the backburner because I thought it was just too simple. It certainly is simple, yes, but I decided maybe simple is also good. It's certainly not any worse than anything else that's already been out there.

First, I'll give the formula. Don't worry. It's simple, painless, and you can perform it easily on your desktop calculator in three steps. (A far sight easier than balancing your checkbook! ) I call the result the "Striking Force" (SF) and it's intended to be a sort-of estimate as to what a cartridge is suitable for. (Note: It won't work for theoreticals like baseballs thrown at 100 mph, because the original calculation assumes that the density of the projectile is at or near that of lead.)

1. Either calculate or look up the kinetic energy figure (in ft-lbs) for the cartridge you're evaluating. Take the square root of that. (For a more realistic/conservative estimate, I've generally used one of the downrange KE figures, say at 100 yards for rifles or 50 yards for handguns.)
2. Multiply the square root of the energy by the bullet diameter, in inches.
3. Multiply the result of #2 by the constant 2.65
4. This is the Striking Force.

Here is a breakdown for the Striking Force values that I have determined so far:

20 or less--Small game and varmints
20 (bare minimum) to 40+ : Deer
30* (bare minimum) to 50+: Large game (for tougher animals a minimum of 40-45 is probably best)
55 (rock bottom minimum) and above: Dangerous game

Okay, there it is. Have fun with it!

(*This is a change from what I originally had. (Trying to do this from memory.)

 

[JimmerJammerMrK]

Is this meant solely for rifle ammunition, or have you used it for pistol ammo as well?

 

[McCall911]

It works for pistol ammunition also. I haven't gotten into scattergun ammo yet.

 

[Grumulkin]

The big question which seems to be unanswered is which metallic cartridge is suitable for which type of game. I have always thought that this was worthy of an answer, but so far nobody has had a really good one.

Actually, it has been answered very well. I would recommend Kevin Robertson's book, The Perfect Shot, available from the Safari Press.

 

[McCall911]

Quote:
The big question which seems to be unanswered is which metallic cartridge is suitable for which type of game. I have always thought that this was worthy of an answer, but so far nobody has had a really good one.

Actually, it has been answered very well. I would recommend Kevin Robertson's book, The Perfect Shot, available from the Safari Press.

That's interesting. Thanks.

But I've seen this: Author A seems to say one thing, Author B says something else, and Author C...well...
Sorry. I just get disgusted sometimes at the number of "experts" who seem to say different things...

Unfortunately, I have no credentials nor any pricey books to sell. I'm just a guy in an internet forum trying to share a small bit of information from my own perspective. I'm a nobody. But I'm sure that if I were one of the recognized authorites, then I probably could embellish this simple thing with a lot of words and sell it like hotcakes.

 

[trapperjohn]

seems very bogus to me. That corrrelation has a linear dependance on bullet diameter (double the bullet diameter and double the killing power) but is only proportonial to the square root of the kinetic energy. This makes no sense, the US army did a lt of studies and determined that kinetic energy was the best indicator of killing power. that being said we all know that penetration is also an issue and penetration is dictated by bullet construction and bullet mass, not bullet diameter.

according to this correlation a 120 grain 44 caliber slug travelling at 200o fps would be TWICE as deady as a 22 caliber 120 grain slug travelling at 2000 fps. Sorry I am not buying it. I think a good case can be made that not only kinetic energy, but bullet mass should be considered, but kinetic energy and bullet diameter, where the killing power is more dependant on diameter than on KE. That is just silly.

 

[McCall911]

Aha. One challenge, at least.

Here's the "full" formula, in all its simplicity:

square-root of (2 x K.E. x density-differential* (lbs/ft^3) x bullet-area (sq. ft)) = "striking-force" (lbs)

(And all this can be abbreviated into what I just gave, above.)

*density-differential is the difference between the density of the bullet and the density of the target. Here, I'm assuming that the bullet is lead (about 708 lb/ft^3 and the target is soft tissue (about 62.4 lb/ft^3.)

There is a formula using momentum which gives the exact same results, but that formula is a little "messier" because it requires the use of a sectional density in pounds per square foot (not inches.)

At any rate, the mass of the bullet is definitely important (hence the kinetic energy) but also important is the bullet's density relative to the target. And it's not really a measure of "lethality" but of net impact force.

So, now, I'm putting my tongue back into my cheek where it belongs...

 

[HM2PAC]

You may enjoy reading "Any Shot You Want" by A-Square.

 

[MCgunner]

Easy way to do it for north America....just buy a .30-06 or better and it'll work in the lower 48 for anything.

The old standby that seems viable for rifles for me (pistols don't quite apply) is 1000 ft lbs on target for deer. However, I know some .22s make 1000 ft lbs on target, but they don't have enough bullet to make me happy with most loads. With a good 70 grain bullet of barnes X type construction out of a .22-250, I can see deer hunting with a .22. Most 55 grain or less bullets are constructed for prairie dogs, though.

If I felt like calculating today, I'd try the formula, maybe later. LOL! I'm a lazy old fart.

 

[MeekandMild]

McCAll, you might be interested in a TKO calculator I stumbled upon.

http://www.beartoothbullets.com/rescources/calculators/php/taylor.htm

 

[MCgunner]

McCAll, you might be interested in a TKO calculator I stumbled upon.

As I understand it, was developed in africa with express rifles and is irrelevant to modern high velocity rifles as it is a momentum calculation. I've even seen this quoted to support the .45ACP over the .357 magnum. It's bunk IMHO.

 

[T.R.]

Lots of hunters forget that modern bullets enlarge quite a bit after impact. In other words, diameter increases. A 130 grain bullet fired from 270 makes a ghastly exit wound regarding deer sized anaimals. This wound is far larger than the unfired bullet still in the box of cartridges. Yet there is always some one who assumes the non-expanding hard cast bullets for 450 Marlin, 45-70, and 458 MAG are more deadly. Doesn't make sense.

I've looked into the chest cavity of many dead animals. Organs are typically badly damaged and diameter of the bullet prior to impact is largely irrelevant. At least with deer sized animals. But I'm not convinced that North American elk or European red deer are armor-plated. After all, no animal can remain on its feet for very long when both lungs are badly damaged and bleeding profusely.

My advise is to use one good rifle cartridge for hunting big game such as .308, 30-06, 7mm-08, 280, etc. As the animal increases in size, shoot more than once! A big herd bull elk can not stand up to two well placed chest shots from any of these cartridges. Two shots from .308 does far more damage than one shot from 300 Weatherby. This fact is seldom spoken.
TR

 

[McCall911]

McCAll, you might be interested in a TKO calculator I stumbled upon.

As I understand it, was developed in africa with express rifles and is irrelevant to modern high velocity rifles as it is a momentum calculation. I've even seen this quoted to support the .45ACP over the .357 magnum. It's bunk IMHO.

It is bunk if you try to apply the TKO outside its intended limited usage for large African game. And the SF also favors the .45 ACP over the .357 Magnum in this regard, but not by so wide a margin.

For instance:

.357 Mag--125 grain bullet at 1240 fps (427 ft-lb KE)--19.5 lbs "striking force" / 7.9 TKO
.45 ACP--230 grains @ 815 fps (339 ft-lb KE)--22.0 lbs "striking force"/ 12.1 TKO

The SF would suggest that the .357 Magnum with such a light loading would be on the low side for deer, but the .45 ACP would be right in the "sweet spot" for this usage. However, range would not be more than 50 yards for either cartridge.

Here are some more examples of the SF that have to do with hunting and not the Great Handgun Caliber Debates: D)

.17 Remington--25 grain at 3300 fps (604 ft-lbs KE)--- 11.2 lbs SF
.218 Bee--46 grain at 2100 fps (450 ft-lbs KE)--- 12.6 lbs SF
.223 Rem--55 grain at 2900 fps (1027 ft-lbs KE)--19.0 lbs SF
.243 Win--100 grain at 2790 fps (1728 ft-lb KE)--26.8 lbs SF
.41 Mag (handgun)--210 gr at 1160 fps (630 ft-lb)--27.2 lbs SF
.44 Mag (handgun)--240 gr at 1180 fps (742 ft-lbs)--31.0 lbs SF
.280 Rem --165 gr at 2500 fps (2289 ft-lbs)--36.0 lbs SF
.30-06--150 gr at 2700 fps (2428 ft-lbs)--40.2 lbs SF
.375 H&H--300 gr at 2300 fps (3523 ft-lbs)--59.0 lbs SF

 

[trapperjohn]

according to my calculations a golf ball doing only 100 mph has a striking force of 46, thats better than the 30-06.

maybe ill rethink my deer hunting method

 

[McCall911]

according to my calculations a golf ball doing only 100 mph has a striking force of 46, thats better than the 30-06.

maybe ill rethink my deer hunting method

Sarcasm noted...

Sure, but a golf ball doesn't have the density of lead, which is one of the things the original formula hinges on. The density of a golf ball probably isn't much more than that of soft tissue, if that much.

 

[trapperjohn]

density of the golf ball is about 50% greater than water. the formula you gave that accounted for density didnt seem to work, it gave drasticly different answers than the first equation with the golf ball still winnning.

my main point of contention with this correlation it is much much much more strongly dependant on bullet diameter than it is on energy.

 

[McCall911]

density of the golf ball is about 50% greater than water. the formula you gave that accounted for density didnt seem to work, it gave drasticly different answers than the first equation with the golf ball still winnning.

my main point of contention with this correlation it is much much much more strongly dependant on bullet diameter than it is on energy.

Well, let me see here. We have this:

The United States Golf Association specifies that a golf ball must weigh no more than 1.620 ounces, be spherical in shape and be no less than 1.68-inches in diameter. This is called "The American Ball".

(Source: http://www.leaderboard.com/GLOSSARY_BALLDIAMETER)

The golf ball weighs 1.62 ounces, so the weight in grains is 1.62/16 x 7000
or 708.75. (Hmm...suspiciously close to the 708 number for the density of lead, but pay me no mind. I just got through watching the movie The Number 23... )

And now this:

The golf ball's density is about 1.15 g/mL, between that of regular water
(1.00 g/mL) and that of saturated salt solution (1.20 g/mL)

(Source: http://dwb4.unl.edu/chemistry/beckerdemos/BD025.html)

So if water is 62.4 lb/ft^3 (the same as the assumed density of soft tissue, by all accounts), then this means the golf ball's density is 62.4 x 1.15 or 71.8 (rounded) lb/ft^3.

So the density differential will be 71.8 - 62.4 or 9.4 lb/ft^3.

I noticed that in my original calculation that I'm using on my desktop BASIC translator, I used the momentum (which is the longer way, but it works out exactly the same as the energy calculation because the momentum was squared.) This does not affect the simplified calculation that I gave, but it does affect the long-version energy calculation because the energy value must be multiplied by 2. So here is the corrected long-version energy formula:

SF = sqr (2 x KE x density-differential x projectile-cross-section ft^2)

So if the KE of the golf ball is 34 ft-lbs, and the projectile cross-section is 0.0154 sq ft, substituting into the formula we get:

sqr (2 x 34 x 9.4 x 0.0154) = sqr(9.844) or 3.14 lbs of striking force.

...whew...

So sorry, that's as good as I can do.

If it ain't good enough for ya, then it just ain't good enough!

 

[Bitmap]

First of all, how did you determine the required SF values?

Second, I'll pick on the category "deer." That covers a lot of ground. In the south a whitetail buck might run 85lbs. on the hoof. In the caprock country of TX a whitetail buck could run twice that or more. In Michigan a whitetail buck could be much bigger. If you add mule deer to that category you can get some real monsters.

Bullet construction. A .308 with a 147gr. FMJ would have about the same SF as a 150gr. Corelokt but the results on big game would probably be different. This is more important with high velocity rifles than with big bore low velocity loads but it still can make a difference.

Where are you planning to hit the game? Again on deer, are you planning on shooting broadside through the ribs? Through the shoulder? The California brain shot? Do you have the patience and skill to wait for a spine shot? The requirements for going broadside through the ribs are a little lower than if you shoot him in the north bound end as he travels south.

I'm not the most experienced hunter in the world but I've shot enough game to know that if you hit 5 different deer in what looks like exactly the same spot using the same load you will probably get 5 different reactions. Some will fall in their tracks, some will flinch and stagger around for a few seconds before they fall and some will run 100 yards or more. That can easily make some people think a particular round or a particular load is inadequate for the game it is used on.

Like the other comparisons people often use your method allows some comparison between loads and calibers as long as you use common sense when you look at the results. If you came up with a super cartridge that would drive a .17HMR bullet fast enough you could get an SF way over 55 but I wouldn't want to use it on elephants.

 

[McCall911]

First of all, how did you determine the required SF values?

That's a really good question, and here's where I need to fess up.

Like I say, I've used this for some time and I began to notice some patterns. In my pre-computer days, I had notebooks half full of henscratchings where I'd written down the results from the calculations I'd done on my pocket calculator. For deer, I remember what I had read in Frank Barnes' "Cartridges of the World" about the 25-35 Winchester being about the minimum for use against deer. I looked back on my tables and noticed that the 25-35 from my calculations had a "striking force" value of almost exactly 20. "Aha!" I said. "So let's call the minimum deer value 20!" Soon afterward, I learned that the minimum caliber allowed for African dangerous game was the .375 H&H. I noticed that my calculations for the .375 H&H was about 59, so I set a "rock-bottom minimum" of 55 for this usage. Honestly, the process for my evaluations wasn't any more scientific than that.

Because it's so "unscientific" I didn't really put a whole lot of stock in it, to be perfectly honest, but for some reason it does seem to hold some water. It does leave out a long list of variables like penetration, expansion, etc. not to mention where to place the shot for maximum terminal effect. As cheesy as it is, I don't expect anyone to take the "striking force" completely seriously or to rely on it entirely. On the other hand, most of its results are hard for me to completely ignore! :banghead:

Oh, yeah. That .17 caliber bullet would have to go at a sizzling 16500 fps to qualify as an elephant cartridge, according to the SF. I couldn't imagine the enormous pressures that would be required to generate that kind of velocity!

 

[GunTech]

I have yet to see a formula for calculating the appropriate cartridge that was worth anything. For a start, even judge subjectively, there are many views on what is sufficient for game - the recent threads on 223 for deer come to mind. Most consider the round inapproriate and yet hundred of deer are taken every year with this round.

Also in the factor is the quarry. Is it laying down relaxing, or pumped full of adrenaline and running.

How about the skill of the shooter. Wherer an animal is hit has a lot to do with effectiveness.

In fact, there are som many variables to the target animal that any 'formula' puporting to determine appropriate cartridge is highly suspect.

And how will you validate you model? What data are you using?

 

[McCall911]

And how will you validate you model? What data are you using?

Everything has been explained already. And, yes, I realize the numerous limitations. Countless limitations. But still the patterns remain. I just thought I'd share it, FWIW, but I'm not forcing it on anyone. It appears that some are interested, if just for giggles.

Gee, I should've played Chuzzle instead.

 

[quicktime]

Put down the calculator and pick up the rifle. Go to the range

 

[McCall911]

Put down the calculator and pick up the rifle. Go to the range