Momentum vs. Impact Energy
 

An earlier thread focused on " minimum impact energy" for a clean kill.
How about a Taylor Index Recommendation of:

17-20 for black bear and deer
20-40 for elk and grizzlies

See which calibers make the cut using the Taylor Index:

http://www.loadammo.com/Topics/July02.htm (Push thru to charts at bottom!)

North American hunters appear to be pretty well fixated on kinetic energy; however, here is a different viewpoint that encapsulates two of the three components of " killing power" put forth by P.O. Ackley (Kinetic Energy, Momentum, Shock). All we need now is a computation for hydrostatic " shock" to work into the mix.

Any thoughts?
[Boo, Hiss, Big Bore Drivel, Nonsense, Where' s Africa?]
Helps to explain why the Marlin Guide Gun in 45-70 or 450 Marlin is a favorite in Alaska (the " Africa of North America" ) :D

Never Go Undergunned,
EKM

RE: Momentum vs. Impact Energy
 

The Taylor index is DESIGNED to give bigger diameter bullets the edge. Since bullet diameter is in the formula, the bigger the diameter, the better it scores.

Just goes to show that there is no perfect system. Foot pounds is weighted to smaller grain, faster shooting bullets and the Taylor index is weighted toward heavier/fatter bullets. Both are true, but are both only a " statistic" derived by math from a group of numbers.

By the Taylor index, the 7mm mag is below acceptable for elk at 100 yards with a 154 grain bullet. I would be that 95% of the hunters on this forum that have shot a 7mm would dissagree strongly with that premise.

The Taylor index is another piece to the puzzle and does shine is very true when comparing big slow bullets (which the ft lbs formulas discount), but foot lbs also have their place as piece of the puzzle.

I suspect when talking about " killing power" the Taylor index is more accurate for calibers from the 30 calibers and up and foot lbs have more meaning from the 7mm calibers on down.

Just like there is no way you can move a 50 grain bullet fast enough to be a good elk bullet no matter how fast you push it, I bet there is a velocity too slow for the big bores to be effective, even though both mathmatical numbers might suggest otherwise. For example, would you consider a 350 grain bullet that has slowed to 500 ft/sec still an ideal elk killer? I wouldn' t, but the Taylor index still gives it a score of 22.5 (if I did the math correct). If that is true, then a 350 grain bullet moving 500 ft/sec would be more effective than the 154 grain 7mm moving 2966 ft/sec at 100 yards. I don' t believe that. ON the other hand, you can make a 50 grain bullet look as good as a 350 grain bullet using ft/lbs. Don' t believe that one either.

RE: Momentum vs. Impact Energy
 

Those calculations look like he came up with his formula while he was sitting on the crapper one night just before going to bed. It just doesn' t make any sence. The KE numbers do not tell the whole story but I feel it is better to use the KE numbers than this formula.

However none of them take into account bullet construction, sectional density, round nose or spitzer, and a number of other factors. I think if we figure the KE and the momentum of a given bullet and put them together to figure out which cartriges to use we would be better off then using the formula on the link. Momentum will give a better indication of how well a bullet will penetrate and KE will give a better indication of how that momentum and KE is going to be transferd to the animal.

RE: Momentum vs. Impact Energy
 

A few points of interest:

(1) The 416 Rigby (with a 400 grain bullet) wins on BOTH Kinetic Energy (ft lbs) AND Taylor Index scores and it is a big bore not a small bore speedster.

(2) Painfully missing are cartridges BETWEEN the 30-06 and the 416 Rigby: 300 Win Mag, 8mm Rem Mag, 338 Win Mag, 375HH -- 30/378, 338/378, 378 Weatherbys -- 338 & 375 UltraMag.

(3) Do you, for good reason, fear a " life and death" encounter with the animal you are hunting? Then the Taylor Index may be the number you are looking for.

(4) Does your choice of game have no choice but to flee from your advance with out a fight? Then Kinetic Energy may be the number you are looking for.

(5) I found a free reloading/ballistics program that in addition to all the other " wow" stuff it does, will also calculate Kinetic Energy and Taylor Indexes and provides a Taylor Index Game Suitablity Table with game types down the left side and ranges across the top at http:/www.HuntingNut.com
-----------------------------

Hmmm....
Having BOTH High Kinetic Energy and High Taylor Indexes, sounds like......:D

Never Going Undergunned,
EKM

RE: Momentum vs. Impact Energy
 

My thoughts exactly. It looks like they' re trying to make a better system but based on the 7mm numbers I think they still have some work to do. A 7mm is an great elk gun.

RE: Momentum vs. Impact Energy
 

The 416 Rigby wins in both catagories because it has speed and size. I totally agree on dangerous game. I would rather have a 416 if being charged by a brown bear or cape buffalo than a 7mm mag, But I will choose the 7mm for an elk at 250-300 yards. My handloads of 175 gr noslers starting at 2900 ft/sec would have a Taylor index of only 19.2 at 100 yards and only 16.8 at 300 yards. I think a minimun of 20 is a overly cautious for elk. I know my load gets the job done out to 300 yards.

As you say, it is good to have both indexes to compare.

One point of confusion. The mathmatical formula looks to me like you are supposed to mulitiply by 2 as the last action. However, if you do this, you get twice the calculated values, so I assume this (2) means something else.

As it works out by his chart, this is the correct formula

Taylor index = bullet wt (gr) divided by 7000 X velocity (ft/sec) X bullet diameter

RE: Momentum vs. Impact Energy
 

I didn' t look at the charts or the formula, but from reading the replys, I think I might understand what' s going on here.

In terms of definitions, momentum and KE are one and the same. Just to get that out of the way, it' s the ability to do work, or a mass at a velocity, tomato tomoto.

HOWEVER, when we talk about killing things, in terms of instantaneous death, it all depends on hydrostatic shock, and as txhunter58 pointed out, the bigger the bullet, the bigger the advantage. Basically, you' re just vibrating them to death, a wave of energy is transferred through their body until it reaches the CNS, and the force exerted upon it shuts things down. In these terms, a scenario of hammers and nails is appropriate: if you drive a nail into a wooden wall, how much does the wall vibrate? It will quite a bit, but some considerable amount of energy is lost to the fact that the nail penetrates the wall, this energy is absorbed by the wall still, but over a period of time, where to cause a vibration, an instantaneous shock is required. Now, remove the nail and whack the wall with the hammer, pending you don' t bust through the wall, it' s going to shimmy and shake like Elvis and a hound dog. All of the energy is instantaneously (not perfectly instantaneously, as an impression is made in the wall, that will rebound to some extent, and the wall as a whole will flex and rebound some, but for all intensive purposes, the transfer is instantaneous). SO, we really shook things up, and a high energy shock wave is heading up the wall, throughout the wood, which eventually dissipates it completely, however, in a living body, the wave would translate to the CNS, shake the heck out of it, and it would shut down just like turning off a lightswitch.

Now, the thing of it is, maybe you don' t have enough resultant energy upon reaching the CNS to shut it down, maybe your bullet broke up upon impact so it didn' t intantaneously transfer its energy, maybe..... the variables are endless, that' s why we hunt with high powered rifles and aim for a spot barely larger than an apple, if the shock wave isn' t enough to do the deed, blood-loss has to, or drowning and oxygen deprivation of the brain and body.

RE: Momentum vs. Impact Energy
 

Geez.... I guess I should throw away my bow. It' s just to dam slow !;)


>wink , wink, nod , nod<

RE: Momentum vs. Impact Energy
 

No Mercy,
Ah, the pitfalls of reading off of the tail end of the thread.... and then turning to Mr. Webster --- it don' t work in this case.

This thread starts with P.O. Ackleys three main components of " killing power" --- (1) one theory LABELED " Kinetic Energy" -- the nice simple ft. pounds theory advocated by most NA hunters.
(2) another theory LABELED " Momentum" -- the negative results associated with a critter " stopping" a big, heavy, wide bullet as advocated by many DG hunters.
(3) another theory LABELED " Shock" -- the hydrostatic shock you allude to.

Several of the people who were discerning a differenc between " momentum" and " kinetic energy" were talking the theories that were grounded in the start of the thread and the references therein.

While Mr. Webster MAY call Kinetic Energy and Momentum synonyms they are NOT the same if you read the theory, math and philosophy and experiences behind each label.

I' ve followed your stuff -- you' ve got some nice rifles in some real decent calibers and don' t appear to be afraid of the big stuff. Just gotta point out that I think you missed the intro. Your opinion is valued though.

Never Go Undergunned
EKM