Home Forums Hunting & Shooting Ask The Gunwriters Penetration versus speed of impact

In this thread http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/3453863#Post3453863 :

I am not surprised, because I have heard that before, but I am very doubtful. I also doubt that this has ever been proven with properly planned and controlled experiments.

From a theoretical point of view I think we can distinct 3 different cases :

1- Bullets with a solid, non expansive, non deformable structure, say like a "Monolithic Solid" and properly stabilized by twist and shape.

In this case, I fail to see why the penetration would not be a constantly growing function of impact speed.

The reasons are that if bullet "A1" has an impact speed of say 3000 f/s and same bullet "A2" has an impact speed of say 2500 f/s and a penetration of "P2" inches. Say that "A1" penetrates "P1A" inches after impact, before it slows down to 2500 f/s, its total penetration should therefore be equal to P1A plus the same penetration achieved by bullet A2. Therefore : P1 = P1A + P2 thus showing that the penetration of this kind of non deformable bullet is constantly increasing with speed.

2- Bullets of the classic expansive structure, say like a "Remington Core-Lokt".

In this case, I would expect the penetration versus speed to have the shape of a asymmetric bell, expansion being at its maximum for a certain "optimum penetration speed", and decreasing thereafter as the impact speed increases and the bullet expands more and looses more and more matter/weight in the initial stage of the impact.

3- Bullets with an expansive front, but which eventually loose the front "petals" when impact speed is above a certain threshold, with only a cylindrical indestructible shank remaining thereafter

These bullets should eventually behave like bullets of type 1- ; that is, after they loose their petals and therefore have a penetration which constantly increases with the speed of impact.


At this stage, I do not see why practical phenomena would lead to different results for the 3 bullet types considered.

What do you think ?


PS - I just now became informed of the existence of a previous thread in the Fire which deals with a similar subject and which I have not had the time to read: How many believe you can make a bullet deadlier by slowing it down? http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/1907332/1

Nevertheless I shall be happy to read your comments and counter arguments if you disagree with me.

Volumes have been scribed on the subject when actually it is a very basic set of facts..

All of the above scenarios can be controlled. and yes in some cases slowing a bullet down will make it much more effective in that the integrity of the bullet is not compromised..

It's a very good idea to try to understand how bullets work, and to try to match the bullet to the task. Mainly what I think about it is that we probably don't know as much as we should about wounding mechanics, and that the issue will continue to be debated.

Within what we do know--or think we know--I think it is fair to say that the kinetic energy of the bullet gets mainly converted to crushing and tearing tissue, and to stretching surrounding tissue. The former creates the permanent wound channel and the second creates bruising. Slower, heavier bullets do more of the first, and faster smaller bullets do more of the second. For slow heavy bullets, the total volume of the wound channel is pretty well proportional to bullet KE. So for the same KE, big fat wound channels tend to be shorter and skinny channels tend to be longer.

The best data I have are from the famous Gary Scuichetti study using 30 caliber 180 grain bullets. His results are shown in the chart.

What's not shown in the chart is penetration at relatively slow speeds. It tends to be much greater, because the bullet does not open.

Vertical axis is penetration in inches, and horizontal axis is impact speed in FPS.

Thank you for your comments.

I agree with what you say. It is entirely consistent with my case 2- above (expanding bullets like Remington Core-Lokt) when the speed is greater than the "optimum penetration speed".

Above that optimum impact speed, penetration does decrease with speed, however, under that speed, penetration must increases with speed.

I agree that for many "cup and core" bullets without a bonded core, one is very likely to be above the "optimum penetration" speed, particularly with a magnum cartridge at short distance.

Nevertheless, the blanket statement that penetration "always decreases with the speed" does not appear accurate, hence my opening of this topic.

For the most part, I think we agree. On this point, I think we have a difference.

If you average the data for several cup and core bullets, you get the chart I've posted below. Averaging lets you see the underlying trends when the data are fairly noisy, which these are.

It sure goes against common sense, doesn't it?

When you get to monometals, like the Barnes X, I think the same statement still applies. Below a minimum impact speed, the bullet does not open. So it makes a very long, skinny wound channel. At 1600 FPS, the bullet will penetrate more than it does at 3000.

Solids? Heckifino what happens.

Outside the range of about 1500 FPS to 3200 FPS? Don't know that either. Surely you get to a point at lower speeds where less impact speed yields less penetration, but that's outside our normal operating range.

Nothin like Graphs and Charts !!!

Don't know this fits the discussion or not, but to me it speaks volumes.

Over the last three years I've shot about 60 feral hogs, all but a very few with CB shorts. Two additional were shot with short hollow points and a third with LR SVRN. Most of the shots were taken within 10 yards. Most were broadside neck shots.

CCI CB shorts do not expand. They will deform mildly from striking bone, mostly in the form of what looks like random tool marks, or experience slight flattening of the nose. On hogs weighing less than about 100# the bullet will penetrate the neck thru and thru, vertebrae included. HiVel HPs will not exit the vertebrae.

CB shorts will penetrate the skull, brain and aft cranial structure to deposit in the neck muscle in hogs up to about 250# on frontal shots taken when the aspect is near 90* to the plane of the skull. In English, wait until their nose is in the dirt to shoot. LR SVRN will do the same and a little more.





A .44 Mag paper patched bullet of 300 grains and pure lead, impacting at ~1,400 fps will break a fore leg, 3 ribs, clean out the heart, two ribs, the off side fore leg and come to rest under the hide on a large deer, retaining 98% weight.



Extreme examples I guess, but slower has it's advantages when well placed. One of the things missing in the discussion above, IMO: Bullet stability during penetration. Round nose forms have a distinct advantage because they are less prone to tumbling. When any bullet tumbles, the wound channel is nasty, but not that deep.

Just read an interesting article by Boddington in Rifle Shooter, which kinda relates to this subject...taken to the extreme.

He wrote about the .577, .600 and .700 Nitro Express.

Of interest, he noted numerous occasions in which elephants took both barrels of these literal cannons to the head, and ran away seemingly unscathed. Concluded that in such instances the ammo was not performing up to specs regarding speed, coming in by about 200 fps under, at roughly 1800. This apparently made all the difference in performance.

The greater the frontal area of the bullet, the more critical is sufficient speed to effect penetration.

On the other hand, we've been reading articles this last year or so about the remarkable performance of ultra high speed - light for caliber bullets, specifically the Barnes Tipped TSX.

As noted in earlier posts, my own experience with these is limited to one elk, shooting Federal Premium 130 TTSX in 300 WM, rated at 3600 fps. About 80 to 100 yard shot. Through the shoulder square on, about 6" below the spine. No pass through, but lungs were destroyed absolutely. It never drew another breath, evidenced by the fact that although it ran about 40 yards, it didn't leave a drop of blood anywhere.

The other elk I've shot was at 50 yds using 200 gr. Sierra Gameking, about 2900 fps, from the same rifle, and never saw even a flinch. It eventually just flopped. The previously mentioned kill with the 130 most definitely elicited a reaction from the bull, as it bolted hard and immediately.

I don't profess to know the physics involved, but I suspect that hyper-velocity behind proper constructed, but relatively light for caliber bullets is taking the science to an entirely other level, perhaps not yet fully understood.

Is there a co-relation between speed and shock that is not accurately measured in "pounds/sq. ft." For I believe the reason that bull did not spit out blood as is typical of a lung shot because the shockwave that went through his chest was so severe that it literally stopped everything completely, specifically his diaphragm from functioning.

The extreme example of this is the rail gun with which the military is experimenting. An 1" x 18" bolt of titanium, with no warhead of any kind, shot at something like 6000 fps, will destroy a tank utterly and thoroughly.

What is the science happening here? And is it applicable to so-called "hyper velocity" bullets?



FWIW.

Too many variables for one answer to the one question.

� To penetrate, drag must be overcome. In any medium, drag increases in inverse proportion to the square of the velocity.

� The faster the impact speed, the tougher the bullet has to be to resist deformation and thus to penetrate.

� etc

This is a learning process......I note what some guys,using the TTSX at "varmint cartridge" velocity say about what it does.Dave Scovill wrote of this about a year or so ago in Rifle Magazine,and his results with the 130 30 cal ,and 120 7mm.African skinners commented they had not seen so much damage from a rifle.

I think Dr Howell raised a crucial point when he said that the higher velocity required a tougher projectile to facilitate penetration,ie stand up to the high impact velocity and still penetrate.

The reason this may be new stuff is because until Barnes came out with the X,there were very few commonly available bullets truly capable of expanding and holding together at such high impact speeds,and maintaing their integrity to continue penetration.Guilding metal jackets and antimony cores of standard bullets, designed for the general run of common cartridges were (are) not capable of withstanding these impact velocities without disintegrating or having their integrity compromised.Some see this as "good",and I suppose it might be on smallish animals,but never cared for it in a BG rifle.Now that Barnes TTSX in light weights are available to many more folks,many are seeing how they work at standard velocities from stuff like the 7/08-120.But start that same bullet at 3500 fps,things seem to change quite a bit.You simple can't duplicate the performance with standard CC bullets as a general rule.

We got a hint of this stuff back in the 80's when friends and I started using BBC's.I also corresponded with other BBC users from all over;generally we noticed the same things.Started at high velocity,they were bombs.You could drop down in bullet weight,start them at higher velocity,drive them into elk(or deer or moose or brown bear,etc) size game at any distance,and still hold over 90% weight retention,broad frontal areas,and deep penetration.Maybe not as far as an X but still plenty.

We used a lot of 140 7mm,and 165 30 cal driven to 3200-3300 fps,and so long as impact velocity was high,got a lot of those "lights-out" type kills;as distance increased some of the "switch-off" effect was not there(due to loss of velocity)but damage was still apparent.One elk guide,noting the damage from my companion's 300 Win Mag loaded with the 165 BBC at 3250,said he had seen a couple hundred elk killed with the 300 WM,and had not seen so much damage from a 30 caliber rifle.I have had similar comments from other folks when I used them on elk and brown bear.

IMO the effects are in the "speed",but you can't really get it unless bullet structure is up to the task.JMHO on an interesting topic

To Doc's first point, the hardest variable to predict would be the point of impact and therefore drag media...talent of shooter, unpredictable wind drift, target movement, etc...so there are actually infinite points of variability in the problem, making the question problematic and the solution unattainable.

But that also makes the question one that will continue to be asked over several more generations and a perfect log for the fire.

Long before I knew Elmer, when the .220 Swift's advertised 4,000 ft/sec was being touted as the latest magical killer, another writer opined in print that at that speed, no other property of the bullet mattered.

One of Elmer's readers had some bronze rod turned to the right diameter and weight and loaded 'em to that magical velocity. Elmer tested 'em on jackrabbits, with almost hilarious results.

Penetration was no problem, and the darn things were deadly enough. But not right away.

Unless one of those bullets hit a bone somewhere along its travels, the jack just paused momentarily to scratch at the entrance hole with its hind foot, then go back to feeding on sagebrush until it slowly bled to death and toppled over.

I've always agreed with Elmer � I'd like (ideally) for any animal that I shoot to be dead before the bullet stops inside the critter or exits.

Depth of penetration is an asset only to the extent that it contributes to that result.

Dead is more important than deep.

Geoff McDonald from Woodleigh Bullets, told me years ago that when he was chronographing all the traditional double cartridges in the early years of his company, (Many Woodleighs are based on original Kynock designs) the factory loads all fell way short of their advertised velociites, so I am not surprised at Boddington's observations.


JW

As he often does, Dr. Howell has contributed a extremely important point: The resistance a projectile experiences when moving through a fluid (minus bones, that's a fair approximation of a critter's body) is exponentially proportional the to velocity. Double the velocity, quadruple the resistance.

It has been a looooong time since I opened the appropriate book, but the true exponent may even be higher than 2.

This leads to some really counter intuitive results. For example, there comes a point where it is easier to move through water than through air.

"For example, there comes a point where it is easier to move through water than through air"

Wow, you lost me there. I agree that resistance increases with the square of the velocity. But air is a fluid and water is a fluid, water being more dense. I can't see where the resistance lines would ever cross. Can you expound a little? thanks

There was an article many years ago, in Handloader or Rifle, I think, that reported on some German experimentation. Maybe it was in Gun Digest. The conclusion was that a bullet penetrating both sides of the body, creating major damage, at a speed of over 2700 FPS, caused a shock to both sides of the brain at the "same time." This caused much faster kills than slower bullets through both sides or 2700+ FPS bullets through one side. I think it was called something like "paarige reflex."

Bruce

I published such an article by Werner Reb in Handloader or Rifle around 1980 or so.

You have a choice, high velocity that may or may not penetrate enough, but if it does it electricutes'em on the spot, jerks their legs out from under them and eveyone goes WOW!! but if they happen to survive the initial hit and sometimes they do, they bleed internaly and will sometimes make many tracks without blood, find a hidy hole and die and you may never find them..I have seen this on more than a few ocassions...High velocity can be very impressive but not consistent and sooner or later you will have a bad day...it hurts to wound and lose an animal..

On the other hand a well constructed bullet that expands moderatly makes two hole, may allow an animal to run a good ways, as much as a 100 yards perhaps with a double lung hit, but he will leave a very good blood trail and he will be dead when you get to him and even with a lesser hit you will probably be able to track him and get another shot, on the other hand if the bullet is too tough and does not open, you may have a tracking job on your hands and may even lose the animal.

That is what I have seen and is my approach to hunting big game and I don't base that on charts, balistics bla bla, or on all the many articles I have read on the subject, rather on extensive experience in the field by doing a lot killing, and by a heck of a lot of observation on all manor of animals both large and small.

I believe Bullet placement is first and foremost, but proper bullet construction must be appropreiate to allow the first part to work. A reasonable caliber, reasonable bullet weight, and a reasonable velocity, and taking shots at reasonalbe range is what works,..and last but not least is common since as it is the catalist to bring it all together. The rest is hogwash.

I prefer the medium weight bullets in "most" all calibers for the plainsgame, deer , elk and antelope such as the 180 gr. 30-06 or the 160 gr. 7x57 and elk may be shot with a heavier bullet for caliber, and the light stuff with perhaps a little lighter bullet for caliber. As long as one does not go to far in either direction..My point is, it's the extremeist in either direction that wound animals with failed bullets, and they are many.

Also, I have no problem with a responsible person hunting deer with a 222 or a 220 Swift, if they pick their shots at reasonable range and in a open country like Sage brush and they know their limitations and abide by them, and are skilled shots, but their are lots of folks that make such claims and then fail to abide by them because they jump a monster buck going south at 50 yards and take the irresponsible shot that blows a chunk of meat out of the animals ass and they won't find him, but he will not survive and die a terrible death..Such a person should be stringhaultered and gilflurted IMO>...

Ohhhh.... you're making me reach waaayyyyyy back to about 1968!

If my brain hasn't totally betrayed me, it has to do with the fact that the viscosity (or density, or something) of air is less than that of water at slow speeds. So if you put resistance on the vertical axis and projectile speed on the horizontal axis, and graph resistance for both fluids, the air curve starts out below the water curve, but because you're raising speed to an exponent, the air curve rises faster than the water curve.

I think. Maybe. Or something like that.

I am pretty sure of the result though. It was kind of a shock to me.

Ray, all that matters is the simple result you have described.

All this analysis is simply amusement for guys like me, and help in finding things that will work in the field.