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Killing power – Kinetic Pulse – Pellet impact – Wound Channels – Impact Ballistics … long

June 18 2010 at 10:13 AM

Yrrah  (Login Yrrah)
YF

I have been away for a week visiting a little grandson and celebrating his first birthday; and as grandfathers are apt to do, I have been cogitating the dynamics of impact ballistics happy.gif.

Killing power Kinetic Pulse Pellet impact Wound Channels Impact Ballistics

Both Kinetic energy loss and momentum loss to a target animal, are implied in wound channels and killing power.

The relationship seems to go something like this:
The depth of the wound channel is a product of the momentum as it harnesses force (mv/t) per unit area on the head of the pellet to penetrate the tissues.

The cross-sectional area of the wound channel seems to be relative to the kinetic energy expended which causes lateral displacement of tissue at right angles to the pellets progress through the tissues.

The wound channel volume depends upon the cross-sectional area of the wound channel multiplied by its length.

Thus, when attempting to compare killing power of one pellets impact performance to that of another, there may be a case for multiplying the momentum lost in the depth of the wound with the kinetic energy lost in creating the cross-sectional area of the wound channel. the assumption being that killing power is directly related to the total volume of disrupted tissue.

I would like to give a real life example based on research I did and reported here in October 2004.

The data briefly reads like this. Three different pellets were shot over a chronograph at 6 ft from the muzzle to establish POI velocity, kinetic energy and momentum.

Freshly killed (still hot) pest birds were located at the 6 ft mark and shot through, with the pellets then immediately passing over the chronograph which was re-located behind the birds to establish exit velocity, exit kinetic energy and exit momentum.

As the same rifle was used the result reflected a true comparison of the parameters for each pellet type for that rifle in its current state of tune.

The results were:
.22 cal 15.9 gr Exact POI V 898 fps exit 648 fps; POI KE 28.465 ft-lbs, out 14.822 ft-lbs, loss 13.643 ft-lbs; momentum POI 0.0634 slug ft/s, out 0.0457 slug ft/sec; loss 0.0177 slug ft/s.

.22 cal Predator 15.9 gr ( 16.0 gr lost 0.2 gr tip in transit so given a 15.9 gr average) POI V 893 fps, exit 485 fps; POI E 28.15 ft-lbs, exit 8.3 ft-lbs, loss 19.85 ft-lbs; momentum POI 0.063 slug ft/s, out 0.034 slug ft/s, loss 0.02876 slug ft/s.

.22 18.2 gr CM POI V 837 fps, out 531 fps (edit typo); POI KE 28.30 ft-lbs, out 11.393 ft-lbs, loss 16.91 ft-lbs; momentum POI 0.0676 slug ft/sec, out 0.0429 slug ft/sec, loss 0.0247 slug ft/s.

Now for the comparison in relation to this specific case:

.22 Exact: KE delivered x momentum conserved = 13.643 x 0.0177 = 0.2415 = Kinetic Pulse reflecting possible killing power.

.22 Predator: 19.85 x 0.02876 = 0.571.

.22 Crow Magnum: 16.91 x 0.0247 = 0.4176.

In this example the comparison of Kinetic Pulse or Killing Power shows the round nosed exact to be 42 % as good as the Predator; and the Crow Magnum to be 73 % as good as the Predator.

NOTE: In case some are wondering about pellet expansion and therefore frontal area and force per unit area, these parameters are incorporated into the KE and momentum loss to the bird in the above experiment


Discussion: OK, I know dead is dead so we'll by-pass that one and we know that accurate head shots on small animals kill rather well regardless of pellet type. So our focus is in heart lung and marginal KZ strikes.

To kick it off: No, neither I, nor most probably anyone else, has down range data at hunting ranges of say 30 to 75 yards to allow examination of the effects of relative losses of velocity etc within animals of various thicknesses.

So , we might look at the picture as it may be if the pest birds had been big enough, or far enough away down range, to have stopped all three pellets in this test without pass-throughs: then: the exit velocity, KE and momentum would be zero and the KE and momentum lost to the animal would be equal to the POI figures.

So, the Exacts would have a Kinetic Pulse of 28.465 x 0.0634 = 1.8047.
The Predators would show 28.15 x 0.063 = 1.7735
The CMs would show 28.30 x 0.0676 = 1.913.
Then, although there is little difference in the figures, the order is CM, Exact, Predator at this range of 6 ft.

However, we know that the BC of Exacts is significantly higher than Predators or CMs and that .22 CMs are renowned for poor accuracy beyond 30 to 35 yards.

Therefore, I would assume that the further the range and the thicker the animal, the better would be the Exact pellets POI figures relative to the other two and therefore Kinetic Pulse would reflect that and the Exacts would ultimately rule due to better momentum and Kinetic Energy conservation. They are also more accurate at longer range and so better able to deliver to the KZs. ( My experience in shooting a fair number of rabbits at and around 150 yards with just 875 fps MV attests to that).

Summing up: Which pellet will do the most damage, at a particular range, will depend upon which delivers the best combination of momentum and KE. Dead now depends upon that combination being delivered to the vitals in proportion to the size and thickness of the animal.

I commend to you James Hall's Kinetic Pulse in the study of bullet impahttp://www.mindtinker.com/math/kp.html and offer my interpretation based on one specific and certainly not all encompassing study example.

Kind regards, Yrrah ( I'm for bed soon so will attend discussion, if any have read this and made comment, in the morning OZ time ).


    
This message has been edited by Yrrah on Jun 19, 2010 4:28 AM


 
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Herb1836
(Login Herb1836)
YF

Mann's book "the bullet's flight ..." is downloadable via internet

June 18 2010, 10:50 AM 


 
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Yrrah
(Login Yrrah)
YF

Thank you Herb, I shall look into that tomorrow .

June 18 2010, 11:07 AM 

That is good news to me .......... You must have seen my plea and I thank you for following up on it happy.gif Kindest regards, Harry.

 
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Robert Vogel
(Login archer280)
YC

Harry very nice info to be sure

June 18 2010, 12:12 PM 

I will do my best to make use of the info

bob


 
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Jamie
(Login USMCShooter)
YF

Of all the people most capable of quantifying it...you are HE harry!

June 18 2010, 12:59 PM 

I knew there had to be a mathmatical way to at least attempt measurement, and I see that you have captured it, and another of your posts I didn't have bookmarked.....

The only possible diversion of data that I can see would be the media struck by the pellet (target...lol).

I've noted that when shooting birds, crows especially, as they are large enough to retain predators fired at closer ranges, that expansion is typical of anything else I've tested them in....

However, the farther out (lower the velocity) they seem to be, the more the predators penetrate due to slower expansion rates.....and my most recent crow, shot through the center chest, striking the center-plate boney structure, at 97yds, was a complete pass-through.....however, I'm resonably certain it would have been a pass-through with any pellet regarding the expansion possible at that range/velocity....

I was surprised to see that the KE of the predator wasn't greater than the others measured though?

s/f

Jamie

 
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Yrrah
(Login Yrrah)
YF

Edit heading... Jamie your points are quite valid.

June 18 2010, 7:22 PM 

There was so much more I wanted to include in the post to cover many bases but it was long already.

As we have discussed previously, the Predator pellet is definitely a special case. My studies, of which there were many before, when the pellet was being trashed by shooters who had never fired one, showed it to be like Janus with more than one face.

At POI fpe above 9 fpe and 500 fps the .22 expands well in birds and rabbits (and other unmentionable pests).
When shot through some hard media eg., wood, bony plates, they extrude into a streamlined profile and don't expand but penetrate well. ( You may recall our exchange in relation to the armadillos . When shot at low velocity in a media in which they don't expand, they also extrude the head and body and penetrate deeper. This relates to extreme range lower velocity impacts too. Every different shot can therefore have a different result depending upon the impact velocity/ KE and the tissue substance-mix of flesh and bone, type of bone be it plate, irregular or long bone, and the depth of the bone. The latter determines whether or not some expansion has already taken place and/ or whether the poly tip is still in place when the pellet reaches the bone.

Tom May, ex US paratrooper, developed a unique pellet that adapts its own behaviour for best results according to circumstance. ...........

Kind regards, Harry.

PS: Now Gamo is/ is trying to cash in on it and is probably succeeding. They stole the USA design and even the advert word for word. The court case is now being drawn out thus favouring Gamo of course. .


    
This message has been edited by Yrrah on Jun 18, 2010 7:28 PM


 
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The Verminator
(Login TheVerminator)
YC

Janus is right, Harry..

June 18 2010, 9:31 PM 

I am forever amazed at the adaptability of the Predator. It really does work in fascinating ways! TV

 
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Herb1836
(Login Herb1836)
YF

RE: "media struck by the pellet"

June 18 2010, 11:31 PM 

Absolutely!

In order for a pellet to mushroom it is about how fast the pellet decelerates. It can lose a lot of energy quickly either because the pellet was shot relatively fast, or because the medium is relatively hard to penetrate.

Shoot a pellet at 300 fps in concrete and it will melt into a blob. Into water and no expansion is visible.

Concrete > soap bar > flesh > water

So a soap bar or wax overestimate the amount of expansion in flesh. Shooting into water underestimates the expansion.

Herb1836


    
This message has been edited by Herb1836 on Jun 18, 2010 11:51 PM


 
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Jamie
(Login USMCShooter)
YF

Thank you Harry....we vindicate this pellet very well I believe...

June 19 2010, 4:53 PM 

However, just another reason that Gamo get none of my money...for any reason...whatsoever.....I've shot their guns, and when properly tuned, will run with anything made...but their ethics are of the sort that leave me cold....

s/f

Jamie

 
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