Posted: 11/21/2005 8:56:25 AM EDT
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.40 Caliber Pressure Wave Effects We had an opportunity this weekend to perform an informal field necropsy on a 180 lb 7 pt buck shot with a 135 Grain .40 caliber Nosler JHP at approximately 1350 FPS impact velocity. Though fired from a muzzleloader, this impact velocity closely approximates the impact velocity of the same bullet fired from a .40 S&W. This load produces one of the larger pressure waves available from JHP ammo in 9mm, .40S&W, .45 ACP, or .357 Sig. This buck was shot during a special youth-only hunt, and the young hunter was gracious enough to allow a couple of scientists access to his deer. The effects of the pressure wave on tissue were impressive. The bullet entered just in front of the third rib (counting from the back) on the left side, pulverized a large (1.5” diameter) on the inside of the rib cage and in the liver, entered the left lung producing a large (1” diameter) pulverized region, entered the right lung producing a pulverized region that gradually shrank in size to the recovered diameter of the bullet (0.58”), exited the rib cage just in front of the 11th rib (counting from the back) and was recovered in the muscles of the right shoulder. The direction of the wound agrees with the account of the shot that the buck was mostly broadside, but angled slightly away with his head down grazing. According to the PCC-only view of handgun bullet wounding (espoused by Fackler/IWBA adherents), the expected wound channel (which assumes crushing is the only mechanism) should be roughly cylindrical in shape, and have a diameter roughly equal to the recovered diameter of the bullet. The volume of this expected wound channel is widely known as the permanent crush cavity (PCC) and given by the frontal area of the recovered bullet times the penetration depth (12”). This gives an expected wound volume of 3.17 cubic inches. What we actually observed is a truncated cone region of pulverized tissue with a diameter of 1.5” on the entrance side, and gradually narrowing to 0.58” on the exit side of the rib cage. The actual volume of this truncated cone of pulverized tissue is 12.18 cubic inches, or nearly 4 times the volume predicted by the PCC-only view of wounding via handgun bullets. In addition, we observed a region of severe to moderate hemorrhaging along the wound channel that was 5” in diameter at entrance, narrowed to roughly 3” in diameter at the medial surface of the left lung and gradually shrank in size to merge with the bullet diameter where the bullet exited the rib cage. This region of hemorrhaging has an approximately truncated cone shape with a volume of 119.3 cubic inches. We believe that the pressure wave is responsible for this hemorrhaging, though we cannot rule out the temporary stretch cavity for some regions. However, the 5” diameter of hemorrhaging of the muscular tissue surrounding the entrance wound is much larger than the expected TSC at this point. This is the effect that hunters associate with high-velocity rifle bullet wounds and refer to as bloodshot meat. Since the pressure wave is more strongly directed backward than the TSC, it makes sense that this hemorrhaging is due to the pressure wave. We also observed mild hemorrhaging along the abdominal walls and rear rib cage on the right side. This is the area directly opposite from the entrance wound, but considerably rearward from the point where the bullet exited the rib cage. Thus this region was out of reach of both the permanent crush cavity and the temporary stretch cavity, and it seems that the most likely cause of the hemorrhaging was the pressure wave. Inspecting the site of the shooting revealed that the deer ran 54 yards (straight line distance) from where it was shot to the point where the carcass was recovered. This is in good agreement with our empirical models which predict the average drop distance from the IWBA-type PCC volume and the peak pressure wave magnitude. In spite of the absence of an exit wound, there was an extremely profuse blood trail spread along the path the deer ran. The wounds we observed for the 135 grain Nosler JHP are very similar to those observed in earlier studies with the 115 grain Triton Quik-Shok at .357 Sig velocities. In both cases, there is substantial tissue damage and destruction beyond the tissue crushed directly by the projectile. These two loads generate comparable pressure waves. The tissue damage we observed from the 135 grain Nosler JHP is markedly different from that which we have observed on earlier occasions with lower pressure wave bullets such as the 147 grain Winchester 9mm bullet at 9mm velocity levels. The tissue damage due to the 147 grain 9mm bullet is very much in accordance with the PCC-only view espoused by Fackler/IWBA adherents: a nearly cylindrical region of crushed tissue with a diameter well approximated by the expanded diameter of the bullet. There is little tissue damage beyond the tissue crushed directly by the bullet. This same 135 grain Nosler JHP bullet is also available in 10mm. We estimate the pressure wave in the 10mm Double Tap loading to be 50% larger than the pressure wave generated at 40 S&W velocities. Interesting. The performance potential of this bullet is almost enough to make me trade in my .357 Sig. Michael Courtney |
We've done some lab tests with .45 bullets at .45 ACP velocities and did not learn anything that can't be inferred from published sources. Most .45 ACP rounds that expand reliably create moderate pressure waves, not the highest, but not the lowest either. Michael Courtney |
I think you misunderstood. .40 S&W and .357 Sig perform very comparably, and it is only in the less common potential applications that their subtle differences become important. The edge in penetration, longer range shooting, and recoil go to the .357 Sig. The edge in the ability to load snake shot goes to the .40 S&W. My point was that the 135 grain Nosler in the 10mm would probably be worth upgrading from .357 Sig, if only Sig made a pistol in 10mm. Michael Courtney |
Yes, I misunderstood. Thank you for the input on the 40 vs the 357 sig. |
Thanks. The wound you describe is actually quite unremarkable given the round fragmented. Dr. Fackler noted almost the exact same type of wound in his 1984 article titled Bullet Fragmentation: A Major Cause of Tissue Disruption in The Journal of Trauma. Numerous studies since then have found that fragmenting rounds give the somewhat cone-shaped wound track you found. I am not sure that you have a good grasp of Dr. Fackler's findings if you did not already know this. If you already knew of this effect, than your initial attribution of the damage to the pressure wave, without mentioning to those less well versed on this topic the already well documented effect of fragmentation, is troubling. You would also know that Dr. Fackler has written NUMEROUS times that the TSC can be a significant wounding mechanism in inelastic tissue like the liver, spleen, pancreas, and kidneys. The liver damage you note is, once again, nothing beyond what one would expect. Your calculation of the total crush cavity volume also is simplistic. Dating back to at least Colonel Hatcher's studies 70 years ago, it has been known that bullet shape has an effect on the cross sectional area of the PCC. Duncan MacPherson includes form factors for various bullet shapes to allow calculation of the expected PCC volume (in the absence of fragmentation). You do have a copy of MacPherson's book? X-ray examination of the damaged area would most likely show the presence of metal fragments throughout. Again, it appears that you may be attributing to the pressure wave damage that was probably done by fragmentation. |
The Fackler/IWBA position is that fragmenting can be a major source of wounding in rifle rounds, but the assertion is that fragmentation is not a major source of wounding in pistol rounds because the fragments are found very close to the crush cavity and never have an opportunity to damage much tissue. Here's a quote from http://www.firearmstactical.com/briefs2.htm:
What part of their assertion, "Fragmentation of hollowpoint bullets does not contribute to any substantial increase in wounding effectiveness." is unclear to you?
I know better than to apply findings for rifle bullets to pistol bullets when it is explicitly stated that fragmentation is a detrement to pistol bullet effectiveness, not an advantage.
If tripling of the wound volume was a well documented result of bullet fragmention, it is quite remarkable that the IWBA recommends strongly against fragmenting handgun loads and that manufacturers have been striving for 100% weight retention.
You are right, but it is the technique that the FBI uses to estimate crush cavity volume.
Of course, I have MacPherson's book. Applying MacPherson's model predicts a wound cavity volume of 4.16 cubic inches. This is slightly bigger than the FBI prediction of 3.17 cubic inches, but nowhere near the observed wound cavity volume of 12.18 cubic inches. Fackler has suggested that the TC can increase the wound cavity volume, but this was in the later paper "A reconsideration of the Wounding Mechanism of Very High Velocity Projectiles - Importance of Projectile Shape." Using a model built on the observations of this paper, one can predict the wound volume of 6.97 cubic inches and this is accounting for fragmentation effects. (In this model, fragmention increases wounding only by enhancing effects of the temporary cavity that handgun loads produce, rather than by direct crushing of tissue by fragments.) The prediction including the contribution of the temporary cavity and fragmentation is still much smaller than the observed wounding of 12.18 cubic inches.
I was clear that we were not ruling out contributions of the TSC to observed wounding in some regions, but that we did observe wounding in regions beyond the reach of the TSC. This was the only wounding which was unambiguously ascribed to the pressure wave. Michael Courtney |
The best shape for a given diameter is a full wad cutter. This is true both for producing a maximum pressure wave and for crushing the most tissue. See MacPherson's book, _Bullet Penetration_. The trouble with your FMJ idea is that there aren't many handgun options with diameters comparable to expanded JHP bullets. According to MacPherson, the shape of the expanded JHP is 82% as effective as a perfect cylinder. This is more than offset by the increase in frontal area offered by expansion. Force damages tissue, not energy. The force which initiates the pressure wave at the front of the bullet is equal to the force expanding the bullet. In addition, it takes a relatively small amount of a bullet's kinetic energy to produce expansion, and this fraction is even smaller with some designs that have pre-stressed/pre-cut jackets and/or cores. MacPherson approaches the pressure issue from a causal viewpoint, attempting to predict penetration from just knowing the facts about the bullet (mass, velocity, shape, etc.) His development is impressive, although some of his approximations are somewhat unjustified (he admits this in the text.) My approach is the reverse: once one has measured how much a bullet penetrates and how much mass it retains, it is a simple matter to infer how large a pressure wave is created. Michael Courtney |
In other words, you never x-rayed the damaged tissue and have just ASSUMED that the observed damage is due to the pressure wave rather than fragmentation.  Tell us again what kind of statistically valid conclusions one can draw from a sample size of one... |
Live animal research is widely accepted in biological and medical fields. If an effect is demonstrated in animals, then it is reasonable to conclude it is highly likely in humans also, and the working hypothesis is that the effect occurs in humans also unless and until it is conclusively demonstrated otherwise. Even the IWBA-folks recognize the importance of live-animal testing. In his book, _Bullet Penetration_, Duncan MacPherson writes:
Michael Courtney |
The only tissue that we concluded was definitively damaged by the pressure wave rather than some other effect was tissue sufficiently far from from the wound channel that it was beyond the reach of the temporary stretch cavity. If crushing by fragments was responsible, then there must have been a continuous crush path from the central wound channel to the remotely damaged tissue. Fragments can be ruled out as a causal agent for the remotely damaged tissue without x-ray simply by the fact that there was no path that a fragment could have travelled from the central wound channel to the areas where remote wounding was observed. We did not definitively ascribe the more severe wounding (pulverized tissue) near the wound channel to the pressure wave. This truncated cone of tissue 1.5" in diameter on the entrance side and 0.58" in diameter on the exit side probably had contributions from direct crushing of the main bullet, tearing by the temporary cavity, crushing by fragmentation, and damage due to the pressure wave. Our main point is that this observed volume of tissue greatly exceeds the volume of tissue expected with currently available wounding models. The fact is that the observed volume of destroyed tissue greatly exceeds the expectations of current models that include crushing, TSC, and fragmentation effects but that do not include the pressure wave. We have observed this for several different bullets that all have pressure waves larger than most pistol bullets. In contrast, the observed volume of destroyed tissue is close to expectations for lower pressure wave bullets. This demonstrates that the pressure wave is correlated with damaged tissue volume that exceeds expectations of models that don't include the pressure wave. The additional fact that we observe tissue damage (hemorrhaging) beyond the reach of the TSC and bullet fragments demonstrates that the pressure wave is capable of wounding. Added to observations that the pressure wave can cause incapacitation in 10-20 lb mammals without a permanent cavity, fragments, or TSC even being present, and it is not at all unreasonable to consider the pressure wave a contributor to wounding and incapacitation.
If a previous theory says that an effect does not occur, then a sample size of one is sufficient for showing that it does occur. Likewise, if a theory says that an effect can occur, a sample size of one is sufficient for concluding that it can occur. For example, only one test of the nuclear bomb was necessary to prove conclusively that nuclear fission can be used to make a great destructive weapon of significant military importance. Had Japan realized this after their first observation of the effect (Hiroshima) they could have spared another city (Nagasaki). A sample size of one is statistically valid for showing that an effect occurs with non-zero probability. You are well aware that this is not the only deer in which we have observed wounding from high-pressure wave handgun bullets. Tell me, if we see comparable volumes (> 10 cubic inches) of destroyed tissue in 10 out of 10 cases we have observed shot through the lungs with bullets with comparable pressure waves, what is the probability of the enhanced wounding not occuring? What does it matter whether or not the actual source of tissue destruction is the fragments or the pressure wave? If additional wounding can be predicted by the presence of a large pressure wave, does it matter if the wave itself causes the wounding or if the fragments torn from the bullet by the intense pressure wave at that point cause the wounding? The fact is, with currently available handgun loads designs, all bullets that have pressure waves of comparable magnitude also have significant fragmentation, and the easiest way to tweak a bullet design to increase the pressure wave magnitude is to increase the fraction of fragmentation. The observation of wounding significantly greater than predicted by existing models calls in to question the validity of those models. Some of this additional wounding (remote hemorrhaging) is unambigously caused by the pressure wave. The cause(s) of the larger volume of destroyed tissue are less certain because the pressure wave, TSC, and fragmentation are all possible in this region. But the bottom line is that the current thinking from IWBA/Fackler/MacPherson is that neither fragmentation nor the pressure wave is a significant wounding mechanism. This thinking is wrong and needs to be changed. Michael Courtney |
Doc: Thank you for follow-up. I should have mentioned that I was not seriously suggesting FMJ as a magic bullet solution. |
You are, once again, setting up a straw man and putting words into the mouths of the people whose views you denegrate. This seems to be a pattern. The wound volume models you refer to are for rounds WHICH DO NOT FRAGMENT. The reason the IWBA et al do not like fragmenting handgun bullets is because fragmenting is undependable, and usually accompanied by lack of sufficient penetration. Even the information from Firearms Tactical you linked above states clearly that "With handgun bullets, penetration and permanent cavity are the only mechanisms that can be relied upon." While you claim to have gotten 12" of penetration in this case, the majority of this was through lung, the least dense tissue in the body. What is its' average penetration in other deer you or your team has shot? How much variation in penetration and wound volume does this round exhibit? How many deer have been shot with this round? Once again, your sample size of one is meaningless. It is an interesting anecdote, but it ain't an earth-shaking breakthrough. This morning I shot a deer with a 165 gr. Nosler Ballistic Tip handload fired from my .30-06. The deer was broadside at 73 yards (laser ranged after the shot). The bullet penetrated both lungs and exited. It traversed about 14" before leaving a 2" diameter exit wound. It struck only lung tissue and shattered one off-side rib. The shot never touched the heart. It was also several inches from the spine. The interesting part was that the deer dropped like it had been struck by the hammer of Thor. DRT. Never moved, twitched, nothing. Therefore, we should make certain that ALL law enforcement agenices in the US only issue .30-06 patrol rifles, and always use 165 gr. Nosler Ballistic Tips. This combination will UNAMBIGUOUSLY stop bad guys in their tracks. QED
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caused by the pressure wave. The cause(s) of the larger volume of destroyed tissue are less certain because the pressure wave, TSC, and fragmentation are all possible in this region. But the bottom line is that the current thinking from IWBA/Fackler/MacPherson is that neither fragmentation nor the pressure wave is a significant wounding mechanism. This thinking is wrong and needs to be changed. Then quit bloviating on the internet and GET YOUR STUDY PUBLISHED!
 Let me catch my breath. I found that quotation from Duncan MacPherson humorous. Not because what MacPherson said is incorrect, but because Dr. Courtney apparently missed the very next paragraph. The above citation from MacPherson's book is found in Chapter 3: Earlier Models of Bullet Wound Effects. Here is what the very next paragraph states:
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I refered to three different models. The model which predicts a wound volume of 6.97 cubic inches does include fragmentation. The MacPherson and FBI models do not include fragmentation. However, since these sources have stated that fragmentation is not a significant wounding mechanism in handgun rounds, it is not a strawman to compare their results for not fragmenting bullets, because their explicit assertion is that fragmenting will not add significant contributions to wounding. What part of their assertion, "Fragmentation of hollowpoint bullets does not contribute to any substantial increase in wounding effectiveness." is unclear to you?
But the fact is that blood pressure drop due to these effects is also an unreliable mechanism for causing incapacitation in the short time span of most gun fights (< 5 seconds). Since even these mechanisms are unreliable in the time span in which incapacitation is required, the best one can hope to do with a handgun is maximize the probability of incapacitation. If the pressure wave effect only produces incapacitation 20% of the time for a given bullet and load, then it does add a significant advantage over a bullet which creates an equal wound channel but has a much smaller pressure wave.
You are right to say that the 12" of penetration is not a meaningful average without a larger sample size. On the other hand, we have observed comparable volumes of wounding with every bullet we've used at comparable pressure wave levels. As far as average penetration goes, I can report that the bullet we used consistently produces 10-12" of penetration in calibrated 10% ballistic gelatin, and that we've never seen penetration less than 10" in deer, except where the spine took a direct hit. You should keep in mind that the purpose of the above report was to describe wounding in excess of that expected from existing models, not to infer that the bullet used can be expected to reliably penetrate 12". I would not recommend that bullet for any given use unless the expected penetration range of 10-12" matched the risk assessments and application of the user.
You are right that what you've got is probably the one of the most effective man stoppers available. That bullet and combination would certainly be high on my list, but this is because of dozens of observations I have made of that bullet, not on a single observation. But I do understand that you're constructing a straw man argument in attempting to mock me for drawing unwarranted conclusions from a small sample size. Your attempted mockery by analogy is a strawman on two counts: 1. I have never recommended any bullet for law enforcement use based on that bullet performed in deer. The tests in deer are to study the science of the pressure wave. I believe that ammo selection for any application should begin by narrowing the field to loads which meet the penetration requirements of a given risk assessment or application. I am in agreement with the IWBA's view that most law enforcement applications require 10" of penetration from handgun bullets. 2. You are well aware that we have observed the effects of a number of different bullet designs on a large number of deer, as well as observations in other species. We are most assuredly not basing conclusions on observations in a single shooting event. Michael Courtney |
MacPherson is wrong here. There has been the same "slow and heavy" vs "light and fast" debate amond deer hunters for decades. Visit any hunting forum on the internet and do a search for a thread on "deer hunting with a .223." This subject most definitely incites acrimonious controversy among hunters. Searching for threads on "Nosler ballistic tip for deer" will also reveal plenty of acrimonious debates with some hunters complaining that the ballistic tip does not penetrate adaquately to reliable kill deer, and others praising the bullet for lightning-like kills. Now, one may or may not take a particular side of the debate, but pretending that there is a unanimous view among hunters is simply wrong. Michael Courtney |
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Take a look at big game hunting bullets. Most all of them are the heaviest, bonded, bullets available. So you're saying the whole ammunition industry and hunters' many years of vast experience are wrong. That's a big piece of cheese to swallow. And if you shoot a deer with .223 better be used to breaking your teeth on bullet fragments if you try to eat it. |
Big game hunters want assured penetration because they want certain recovery within 100 yards of the initial impact, and bonded rifle bullets provide this. They are concerned with the recovery of a single large game animal and usually hoping to kill a trophy animal at the higher end of the weight range and also to be able to make the shot from whatever angle is presented. This task is much different from seeking the greatest chance of rapid incapacitation. I've shot hundreds of deer over the past decade in a nuisance damage control situation. Often times we shoot deer in the summer and we shoot many deer in a single evening. Add to this our proximity to swamps and property lines and the prospect of a 100 yard tracking job on a bunch of deer on a hot summer evening in mosquito infested swamps is not very appealing. In contrast to most sport hunters, we want a bullet that creates the most rapid incapacitation possible for the quickest recovery times. Our bullet of choice for the most rapid recovery possible is the 125 grain Nosler ballistic tip in .308 or 30-06 at 3000-3200 FPS. Another load we like a lot is the 85 grain combined technologies ballistic silver tip in 25-06 at 3550 FPS. Using these loads and shots to the chest, we get instant drops (no tracking job at all) over 80% of the time. If I was hunting a single trophy buck in conditions where a 100 yard tracking job is no big deal, I would use a heavier bullet with more penetration. But when incapacitation in under 5 seconds is the more important consideration, the bullets we use provide it very reliably. Michael Courtney |
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That's interesting. But there are always conditions which call for different bullets. For example, if you hunt deer in thickets where you might get small branches in the bullet's path, you want a heavier, slower moving round, or else you'll likely miss the vitals and wound the deer, or miss it completely due to a deflected shot. However, any deer I've seen shot cleanly through the heart rarely goes more than 20-50 yards before it drops and starts kicking. Even with a .22 LR. You must totally be macerating the chest cavity to get a blood pressure drop to the brain fast enough to cause them to drop in their tracks. I'm guessing anything north of the rump isn't edible after that due to fragmentation from bullet and bone. We have a lot of swamp hunting here too. It just means you bring your hip waders and DEET. 
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Also, most ethical sport hunters want a quick drop too. It means less suffering for the animal. So I don't know where you're getting the idea most sport hunters want a semi-killed deer so they can track it. That's every hunters nightmare is to wound a trophy deer they have to track and might not find. They want clean quick kills. |
Of course.
Good point, ballistic tips are an expecially poor choice in thick cover. If you hit even a small branch, they come apart before reaching the target and make a poorly penetrating superficial wound.
I agree. But most center chest shots don't hit the heart. The heart sits very low in the chest of a deer, and a shot that hits the heart directly is within 3" or so from the bottom of the chest. The horizontal centerline is about 9" from the bottom of the chest, and well above the heart. Our habit is to aim dead center, so we very rarely hit low enough to hit the heart. We're typically impacting lungs and major blood vessels.
I don't think it's the blood pressure drop causing them to drop in their tracks. I don't think there is any way to incapacitate a deer by blood pressure drop in under 5 seconds. The immediate incapacitation we see is either the TSC impacting the spine, the pressure wave affecting the CNS, or disruption of the shoulders.
It's not that bad. The backstraps are fine. Usually only the ribs and near-side shoulder suffer significant meat loss. I'll trade 5-10 lbs of lost meat for an easy recovery every time. Michael Courtney |
A deer that only runs 50-100 yards is unconscious within 5-10 seconds of the shot if hit squarely through the chest. There's nothing unethical here, and nearly all bow-killed deer run this far.
I'm not saying that most hunters want this result, and a deer hit squarely through the chest with an expanding centerfire firle bullet is not semi-killed. The deer is dead on its feet, but it takes 5-10 seconds to fall down from blood pressure drop many times. I don't think any hunter prefers a tracking job to an instant drop. However, many are willing to trade the quicker drop of a ballistic tip for the better penetration and less damaged meat of more slowly expanding designs. Some go with better penetration so they can shoot deer from sub-optimal shot angles.
A 50-100 yard tracking job is a quick-clean kill, and almost any competent hunter will find deer that don't run any further than this. Invariable, deer that run and run and run when hit with rifle bullets that both expand and penetrate reliably are hit poorly (gut-shot mostly), Michael Courtney |
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Since you haven't mentioned it, if you do hit a deer, but it runs off, don't chase it or walk after it. That's why they run for miles and miles. If you just sit back where you were and be quiet for a couple hours or carefully sneak off in the other direction and come back after a few hours, the deer will likely be dead about 100 yards from where it was hit. When a deer is shot in a non-vital place, it will bolt then stop about 100 yards into the woods and look and listen. If it doesn't hear or see anything (like a man with a gun walking after it), it will lie down right there and bleed out. Even gut shot deer can be recovered like this. If you spook it after it makes that first stop to assess what the hell just happened, they learn it was you coming after them, and then they get an adrenalin rush and go for miles non-stop. Anything less than destruction of the heart, spine or brain and the deer is going to run and run for miles if you chase it. I've seen where deer have been dumping cups of bright red lung blood in the snow, and run for miles, until gradually they stop bleeding and catch their second wind and make it into the next county never to be seen again. Deer and humans are totally different animals, literally. |