Terminal Ballistics

jingzy

Well-Known Member
I have seen many debates carried out in the rifle and calibre pages, but really, the hole in my pipe is bigger than the hole in your pipe is getting lengthy and sometimes tiresome.

External ballistics is the viewpoint that many people come from particularly when it is anything to downing the 6.5. Lets try to leave calibre out of it at the moment and I am sure some will attempt to go down that route as quickly as possible.

Lets try to debate what actually puts a deer on its arse, other than a spine shot :eek: .

I will start the ball rolling by saying that irrespective of the calibre used, the bullet must deform in such a reliable way and maintain its ability to penetrate at least as far as the vital organs with the diameter of the projectile reaching about 2 to 3 times its original diameter, causing a high level of cavitation on its way through. The underlying issue is to have a calibre large enough to actually go through the animal beyond the vitals, but this needs to be coupled with the correct selection of bullet head.

Discuss:
 
dead is dead, but how you get there is different.

You can have a deer drop on the spot, dead within seconds due to massive blood loss and low blood pressure. Or you can have the wrong choice bullet or calibre, the deer running on and dying over a long period (perhaps 24hrs)of time. Both dead, one humane the other not so.
 
I like this http://www.rathcoombe.net/sci-tech/ballistics/wounding.html set of essays on the subject.

Having said that, perhaps we can boil it down to these points:

1. We select a calibre/bullet combination which can be lawfully used for the purpose required
2. We make the bullet hit the right part of the beast
3. The bullet, having gone in, comes out again regardless of what it hits on the way
4. It comes out significantly wider than when it went in
5. It doesn't fill the beast with bits, or leave it looking like the victim of a RPG attack

As long as those conditions are met, I don't think there's really much to choose between the common deer-legal chamberings used in the UK.

One could argue that flatter trajectory and wind- or obstruction-bucking ability will help with 2. above, but really as long as you know your range, conditions and rifle, is there really much in it?

The debates are entertaining, though!

p.s. What is a 'bullet head'?
 
My thinking on this has very little to do with calibre; purely to do with energy transfer. I think that the correct bullet, fired with a suitable velocity, entering the right point, in any animal will put it down. If the bullet fails to expand then there is no energy transfer. Likewise if the bullet expands too soon the energy is not transfered to the right area, limiting the effects of the hydrostatic shock (though more often than not, still fatal).

When I started stalking all the talk was of correct powder loads for the best accuracy - no one ever though to mention what effect more or less velocity would have when the bullet enters its intended target.

I have seen a 6mm barnes 85g TSX go straight through at close range (<50yds). After eventually finding the doe and inspecting the carcass there was no expansion to speak of (fortunatly the bullet had gone clean through one of the major blood vessels at the top of the heart so she didn't make it too far!). The round was from a series of home loads that shot really well and that I had Chrono'd at around 3300fps (45.2g H414). The same bullet pushed out a bit slower (3050fps) has never let me down. This may have been a faulty bullet; no way of knowing - but I feel a lot more confident with a slightly slower bullet as it appears to deliver more energy in the target with less fragmentation.

Chops
 
Thanks Dalua,

projectile or bullet :oops:

You have given me what others during their whose calibre is better than whose dont. It is not the actual bullet getting to the quarry, it is actually what happens when it is at the business end.

Of course there is obviously a high level of importance in the bullet getting to the quarry, but once it gets there, it has to cull the animal efficiently.

http://www.hawkbullets.com/terminal.htm

This is another site that shows different terminal happenings.
 
bullet choice is the most vital thing of all imo, it allways suprised me that manufacturers don't make more info available about the bullet construction and intended quarry species/velocities. Bullet selection is allways going to be a compromise as i dont think you can get the perfect bullet. If you only shoot roe for instance and you only shoot 100m max and you allways shoot behind the shoulder then you should be able to get close to the ideal bullet but if you then shoot a big red at 250m hit it in the shoulder then how will your bullet perform ?
In my stalking rifles i've been guilty of using what i can get in good supply and i've been lucky but in the other rifles i've tried lots of different types of bullets and can hohnestly say that too heavily constructed bullets will be more likely to give you a runner that will drop before to long but you might not have a good trail to follow, to light a bullet will often give you an animal that can not be followed up at all.
when i was lamping 3 nights a week 2 of the lads that i lamped with used to shoot from time to time, one of them uses a 243 AI and the other a 17Rem both were flatter than my 223 and both were more accurate but both injured more foxes than my little 55gn V max in the end he changed bullets in the 243 and it was devastating on any thing it hit, the rem was a lesson in bullet selection.

Just my 2 peneth worth.
Cheers Ezzy.
 
jingzy said:
2 to 3 times its original diameter, causing a high level of cavitation on its way through.
Discuss:

Hi Jingzy

In any bullet I have recovered from a deer they have never expanded 3 times there original diameter, :eek: close to 2 times at the maximum.

Also remember that it is the frontal surface area of the bullet that is transferring the bullet energy to the animal and creating the wound channel. Basic maths ( Pi X radius X radius= area) radius= ½ the bullet diameter. An example of this would be a bullet of 5mm diameter compared to a 10mm bullet, although the 10mm bullet is twice the diameter it creates a wound channel 4 times the surface area. Therefore a small increase in bullet diameter will give a proportionally much larger increase in frontal bullet area/wound channel.

The other component to consider is hydrolastic shock, it is usually accepted that the greater velocity leads to more hydrolastic shock.

The 22-250 was thought a great slayer for red hinds before the deer act was brought in, I guess that was with the proviso you didn’t hit the shoulder :confused: and put the bullet though the ribs.

I think Eddy post is a good one. Some bullet manufactures do give data on what velocity range there bullets are designed to expand in. But the bottom line is, less velocity equals less expansion leading to smaller wound channel and less hydrolastic shock.

Still if every deer fell dead on the spot when would I get chance to have fun tracking with my GWP. :lol:

Best rgds

Tahr
 
Ezzy and Thar,

I agree with you both on this one and although velocity is a major contributing factor in the end game, I firmly believe it is the capacity of the bullet to expand properly in such a manner as to deliver maximum energy transfer to the animal and create a wound channel to disrupt as much of the vitals as possible.

So perhaps with a lot of the previous posts that we have been involved with, it is actually the choice of bullet that has been the problem for some.

Heres another conundrum then, is there a velocity where a bullet will be more effective than at other velocities. I have read this in the sporting rifle last year and believe that it will be down to bullet construction and its intended purpose. ie varmint, deer, big game.

:lol: Thar, I didn't think that you got any runners 8)

How long to train your GWP and for it to settle down?
 
Also remember that it is the frontal surface area of the bullet that is transferring the bullet energy to the animal and creating the wound channel. Basic maths ( Pi X radius X radius= area) radius= ½ the bullet diameter. An example of this would be a bullet of 5mm diameter compared to a 10mm bullet, although the 10mm bullet is twice the diameter it creates a wound channel 4 times the surface area. Therefore a small increase in bullet diameter will give a proportionally much larger increase in frontal bullet area/wound channel.

Surely this only works if the bullet is flat? Pi x r(squared) is for a cricle. This does not tak into account the acutal frontal area of a bullet. A long target round in 30 cal has significantly more 'surface area, then say a a round nose large game gound in say 6mm - yet the round nose, becasue it is designed to expand will deliver more energy as following expansion it's wider than the 30 cal. Plus the weight of the bullet dictates the energy it carries.

Kinetic Energy = 0·5 x mass x velocity2
or
KE = ½mv2

A wound channel is created by the transfer of energy. The bullet must be given that energy from the charge of powder and must have the ability to transfer it to the quarry. Diameter of round only comes into play when used in conjunction with bullet mass because we are limited to what the manufacturers can provide us with.

If you comapre two bullets from the same calibre, one target and one expanding - yes the expanding rounds does the job we want better. But if taken one step further on and compare two rounds of the same calibre with two types of expanding bullet then we are back where we started. Which ever bullet delivers the right amount of energy to the right place to take th beast down.

I would love to see some ballistic info on say a 80g 6mm ballistic tip (known to have explosive expansion) and a 6.5mm or 30 cal failsafe, when compared purely on energy transfer to target. If the 80g 6mm delivers all of its energy so that it does not have an exit - is it therefore delivering more energy than a 6.5mm or 30cal that leaves a wound channel but still has a lot of energy when leaving via the other side? I think only block of ballistics gel and some pretty fancy measuring kit could tell!

Chops

PS I would love to get a GWP (or any decent deer dog for that matter) but her indoors thinks otherwise :cry:
 
Folks,

This post has really got me thinking (first time in years!) - so I have set about reading through a few of my books on the subject:

Hatcher's Notebook was the first which I have cross referenced with Brian J Heard's 'Handbook of Firearms and Ballistics'. I think Thar and I have both got it right and wrong.

Major Julian Hatcher thought that the wounding effects of a bullet would depend upon its striking energy (kinetic energy). But when testing he found this NOT to be true. He worked on a formula for what he called RSP or Relative Stopping Power:

RSP = Bullet Cross Sectional Area x muzzel energy x Shape Factor

The shape factor was an emperical figure set that he devised and accounted for how a bulleted behaved when striking and entering a specified object. These tests were done around 1935 so ballistic tips and failsafe rounds did not exsist plus all the calibres were pistol rounds.

Over the next few years Hatcher realised that the RSP concept was not quite right. The kinetic energy was wrong as the bullet mass was not taken into consideration. To compensate he altered the formula to:

RSP = Bullet Cross Sectional Area x momentum x Shape Factor

[where momentum = mass x velocity]

Then some medics in the states started adding to the formula by adding a 'hit distibution' index - basically the higher the index number the more deadly the shot placement. This lead to the relative incapacity index still used when evaluating bullets for the police today.

In 1991 testing was done to establish average incapacitation times for various rounds (The Strasborg Tests). The showed that in rounds travelling at <1100f/s (the average speed of sound in air) sectional area is critical to stopping power.

Sorry for the history lesson but I thought it was quite interesting...

Chops
 
Math is good but every dammed deer you hit is a variable unto itself. My rule is that I want as much of the energy the bullet is carrying on impact to remain in the animal, regardless of caliber. When in doubt, long bullets are better.

Shot placement is everything.~Muir
 
Chops,

your idea of the 6mm bullet leaving all its enery in the animal is one that wont necessarily work. If it is a varmint/explosive type bullet and it is frangible by design, the energy could be distributed long before it reaches the vitals, indeed possibly before it gets through muscle and bone. One that is designed to mushroom and retain weight will distribute energy on its way through.

A basic example of this would be a slap with the open hand will sting but will generally not put you on the floor (6mm frangible) However a clenched fist striking you will have a different effect.

:lol:
 
I suspect that the energy thing is a bit of a distraction from the fundamental matter of what makes a deer dead. The deer dies either when blood pressure falls or if the central nervous system is destroyed.

Now, there is no question that energy is necessary to do work but energy in itself does not kill the deer. A bullet that enters a deer at 3000fps and exits at 2000fps having destroyed the heart will kill the deer even if only a proportion of its energy was "dumped" in the deer.

So, energy is only useful to us in respect of its relationship to an ability to do work. It is possible that the majority of the energy expended by a bullet on its travels through a deer is actually employed to deform the bullet rather than on doing work on the tissue of the deer. If you take a Nosler Partition, for example, and try to deform the jacket and detatch and deform the front lead core as you might see with a bullet that had hit a deer you will find it requires quite a lot of energy. If you take the lungs and some blood vessels from a deer I imagine you will find that it takes rather less energy to distrupt them in some significant way.

I would suggest that this is why bullets which tend to "explode" are unlikely to penetrate to any great distance; much of their energy is expended in deforming the bullet. In certain specific situations, though not with deer, this may be exactly what is required.

With that in mind I would be of the view that the purpose of a bullet is to damage the heart and lungs (in the case of a shot aimed at this target) to such an extent that it leads to the rapid death of the deer. How much energy the bullet uses to do this is not important either to us nor, in my experience, to the deer; neither need we be concerned with how much energy is left over after the process is complete.

Based upon this logic I would argue that it is unimportant whether the bullet exits or not, assuming you don't require another hole for a blood trail etc., providing the vital organs are destroyed. Equally I believe that the various arguments concerning the temporary cavity are, at best, built on rather dodgy ground.

I would suggest, therefore, that you pick a bullet capable of destroying the heart and lungs and that you don't worry about what happens with the left over energy. If you need to hit the vital organs through bone or from a difficult angle then you need a bullet capable of "more" penetration than for a broadside heart and lung shot but in the case of UK deer that will be related more to bullet design rather than any measure of absolute energy.
 
Jingzy - I fair point - but that is why we have to think about a bullet delivering its energy to the right point in the quarry. Nice analergy :D .

Caorach - the very act of a bullet deforming must entail it passing its energy on to something. It could be the air, or skin or bone... but that energy has to go somewhere as it cannot just disappear (see Einstein 101) :eek: !

If a round deforms on entering a body but does not hit a vital organ directly, the hydrostatic shock, caused by the energy released from the bullet deformation, will more often than not kill the animal. The pressure wave created can burst blood vessels, both minor and major, and we have a kill.

To say that it is not useful to understand these concepts would seem strange - to understand it or at least to try to understand it (in my case) seems to make logical sense as I like to know what is going on when I pull the trigger and because of previous experience (mentioned before) I do not necessarily trust the bullets will do what they say on the tin...

Chops
 
I'm not really sure about the whole 'hydrostatic shock' and 'hydrolastic shock' thing.

I think it's more to do with making an adequately large hole through an important part of the animal.

In my opinion these various kinds of so-called 'shock' are a highly-scientific-sounding distraction.
 
Chops

If you look at a recovered bullet you will see that its frontal area is to all practical purposes flat, hence why the PiXrXr is valid.

Dacua

Hydrostatic shock is a well known phenomena, if you look at any tests that have been conducted on ballistic gel the amount of “tissue” damage can clearly be seen were the gel has turned “milky”.

There are other theories on what makes an effective bullet that introduce factures other than velocity/bullet weight. But at the moment all over the world it is generally accepted that muzzle energy is the main facture in evaluating the power of a rifle bullet.

Jingzy

“The name of the man that never misses is………………………….Billy liar.” ;)

Shoot enough deer and you will get the odd runner, even deer hit fair and square in the heart a deer can run a fair way; see some of the other posts on here. I have tracked neck shot deer 700 yrds. I use my dog not only for myself but for other guns on my syndicate and when taking odd guest out.

I had her on deer at 12 months but she was 3 before she was fully trained on fur and feather. Some of the GWPs can be hard work but if you know were to look there are more biddable lines more suited for the UK shooter.

Best rgds

Tahr
 
Thar said:
Chops

If you look at a recovered bullet you will see that its frontal area is to all practical purposes flat, hence why the PiXrXr is valid.

Kevin, I don't quite follow your argument here, if you are saying that the formula is applicable to a recovered bullet, ie after the event, how can it be applied to the same bullet before the deformation. Are there not too many variables in the bullets for this to apply, I doubt if a dozen recovered bullets from the same box fired by the same rifle at the same type of animal would all yield the same result. I know you say for all practical purposes but can we mix and match an exact measurement with near enough?

Don't get me wrong i have no alternative solution I am just trying to get it right in my own mind. I would love it if there were a way for us to determine the absolute best bullet for our chosen calibre to expand and do the job reliably time after time.

Reading this very interesting thread I am coming to the conclusion that all the science can only help by pushing us in the right direction. We all know that by using any one of the legally designated rifles, with the correct bullet, travelling at the right velocity and hitting the correct place on the animal the job will be done. We all have our own ideas on calibre, speed, exit wound or not, by this I refer to the fact that some prefer all of the bullets energy to have been used in the beast with the bullet being recovered from just under the skin. That does not make any of us right or wrong, just different to our neighbour, and that is not a bad thing.

Great thought provoking thread.

John
 
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