Book Chapter 11-Home

Hunting Bullet Metrics

Apply Terminal Performance Truth

AFRICA HUNTER QUEST©

Chapter 11 - BULLET PERFORMANCE CONSIDERATIONS FOR HUNTING AFRICA PLAINS GAME

GG: Before we take on generic bullet designs and how they perform, we now need to talk about the actual bullet performance you want. When we talked about the conceptual wound cavity and the factors that comprise a hunting problem definition, I introduced concepts that can be kindly thought of as dots. Now I’m really gonna make you work by forcing you to connect those dots to arrive at how you want your bullet to perform when you go to Africa. Once you decide the performance that is important to you, selecting a bullet design compatible with that performance really isn’t all that hard. Are you game?

D: You haven’t run me off yet.

GG: All righty then. What result do you want from a bullet’s impact on an animal?

D: A recovered one.

GG: Excellent. When you say ‘recovered’, does that imply any concepts and/or strategies that increase the odds of a recovered animal?

D: Shortened time to death. You talked about that with the sheep example. A shorter time to death means the animal doesn’t travel all that far. Conceptually, the shortest time to death is associated with the word ‘stop’.

GG: Yep. What have we talked about so far that likely enhances the prospect of ‘stop’?

D: A big wound cavity volume. Robertson says bigger is better, and bigger produces a quicker death.

GG: Yep. I am now going to add the word ‘effective’ as an adjective to the term ‘wound cavity volume’. Why?

D: You mean effective wound cavity volume?

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GG: Yes.

D: First, that means the wound cavity must be in high-percentage organs essential for the animal’s immediate survival, like the lungs and heart. A large cavity in the stomach could potentially kill it, but likely not in a time frame compatible with recovery.

Second, that means that the cavity should ideally be housed entirely within those organs. For example, having the wound cavity in both lungs would be way better than just one lung, and having the cavity in both lungs and the heart would be best of all.

GG: Absolutely. Have you just identified a shot location associated with high odds of a recovered animal?

D: Yes. The shoulder. Aiming for the shoulder gives the best chance for a bullet to take out both lungs and the heart, or the major plumbing directly above the heart.

GG: Does that shot location provide any other benefit?

D: Yes. It debilitates at least one shoulder, likely both, which decreases the animal’s mobility.

GG: Agreed. You said both shoulders. What have you just assumed?

D: Oh, a broadside shot.

GG: Have you just identified a component of your hunting problem definition?

D: Yes. Shot angle. A broadside shot gives the best chance for a recovered animal because the wound cavity is from shoulder to shoulder, through the boiler room.

GG: Are there any other benefits to a broadside shot?

D: Ease of locating exactly where you want to aim. Probably more forgiving if you miss the aim point.

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GG: Meaning?

D: If you hit too far back, you can at least get the lungs, maybe even the kidneys or the liver.

GG: Any other benefits?

Donny sat and thought. Nothing came to mind.

D: I can’t think of any.

GG: Any dimension considerations?

D: Dimension considerations? You mean like length of bullet travel?

Donny watched GG just sitting there, waiting. “Dimension . . . ?”

D: You mean like a bullet penetrating broadside would travel the least length to do the most damage in the boiler room?

GG: Bingo! It’s the most efficient shot angle in terms of effective wound cavity volume. It penetrates the least and achieves the most. Does that suggest another bullet performance consideration?

D: Effective penetration.

GG: Good for you. You used the word ‘effective’. Why?

D: For the bullet to do any good, it has to get to and through a critical organ or organs.

GG: Very impressive. You have yet to break into a cranial sweat. So, my question to you is this: if a bullet from a broadside shot is retained by the far-side hide, is that considered effective penetration?

D: Good question. The bailout response is I don’t know; I really don’t. But the fact it is retained by the far-side hide is proof that it fully penetrated both shoulders and the boiler room. So in that sense, it demonstrates effective penetration. But it didn’t fully penetrate to the extent of exiting animal.

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GG: Because the bullet didn’t exit the far-side hide, some folks would say not only “no”, but “hell no” to the notion that the bullet had exhibited effective penetration. Any hunting-based reason why they would believe that complete penetration through the animal was the only way for their bullet to perform?

D: Blood trail?

GG: Bingo! Perforate to ventilate. Remove the negative pressure in the lungs to enhance bleeding through both entrance and exit holes. Bleed’em out, then find’em. Sounds good, doesn’t it? Any conceptual problems?

Donny now realized GG had been spoon feeding him. If the Old Man hadn’t used the word ‘conceptual’, he wouldn’t have had a clue. The thought suddenly hit him that everything they had talked about so far had its basis in a conceptual wound cavity: blowfish, guppy, or eel-snake.

D: Not as long as there is a reasonable and effective wound cavity.

Donny saw the Geezer break out into a huge grin. “Bingo!” thought Donny.

GG: Up until this point, we have chugged merrily along under the implied assumption that our bullet expanded and produced a wound cavity. No one has described the wound cavity even in qualitative terms. We have a cavity, and that was assumed to be ok regardless of volume.

We have just asked the question in the form of “How much penetration is enough”? The same question also needs to be asked about wound cavity volume. How much is enough?

Each hunter has to answer both of those questions if there is to be a bullet strategically selected for any defined hunting problem. The answer is highly subjective. There are no right or wrong answers, only trade-offs and compromises. The punchline to all of this is, in very general terms, penetration and wound cavity volume are mutually exclusive performance objectives. A bullet that penetrates forever will typically have an anemic wound cavity volume. At best, the cavity resembles an eel-snake, but could resemble a snake. A bullet that produces a gonzo wound cavity will typically have an anemic penetration. The cavity resembles a pissed-off blow fish. A bullet that produces a compromise between gonzo wound cavity and forever penetration has a wound cavity that resembles a finless guppy.

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D: So, I get to be Goldilocks?

GG: Well said. Only you can determine ‘just right’.

The question I asked about a bullet being retained by the far side hide is really a litmus test or an indicator of where your natural preference for terminal bullet performance resides. When viewed in the context of my gel testing results, I believe a bullet consistently retained by the far-side hide from a broadside shot is a general indicator that it has terminal performance balanced to some degree between wound cavity volume and penetration. For what it’s worth, Taylor was of the opinion that animals expired quicker if the bullet was retained by the far side hide. That opinion comes from playing ‘same and different’ literally thousands of times.

You have essentially said you have no problem with a bullet that exits the far- side hide as long as there is a reasonable and effective wound cavity produced. Can you think of any benefits beside a blood trail for a bullet that performs that way?

D: I’m not sure. Possibly more shot angle options?

GG: Yes. What is the shot angle you would expect that requires the longest penetration to be considered effective?

D: Rear quartering.

GG: Yep. Finn Aagaard, an exceptional PH in Africa as well as a noted author, believed a bullet that consistently exited an animal on a broadside shot through the ribs was well suited for an any angle shot on the same animal. So, once you got over to Africa and saw that your bullet exited on a broadside shot through the ribs on such animals as a black wildebeest, gemsbok, and zebra, could you conclude that it would likely be successful on a kudu in a rear quarterly shot scenario?

D: I would say yes.

GG: So would I. But the results of my bullet testing in 20% synthetic gel indicate an average of about 90% of the total wound cavity volume occurs within only about 50% of a bullet’s total penetration length, regardless of whether the cavity resembles a finless guppy or an eel-snake. Furthermore, the maximum diameter of the cavity typically occurs at an average penetration of only about 5 inches. Any reaction to those test results?

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D: Hmmmm. . . … In a rear quartering shot, you could reasonably figure that most of a bullet’s wound cavity generating potential would be gone by the time it penetrated into the boiler room.

GG: Bingo! So, what can you conclude about a rear quartering shot?

D: Compared to a broadside shot, it’s really not a high percentage one in terms of effective wound cavity volume. Besides, there is greater difficulty in picking out a precise aim point to take out the heart based on the pictures I’ve seen in Robertson’s book.

GG: Agreed. For what it’s worth, I prefer a bullet with performance balanced between wound cavity volume and penetration. My experience indicates those bullets perform well at full broadside, front quartering and full frontal shot angles. Those shot angles are at least 90 to 95% of the total shots you would likely take on a trophy hunt. Care to summarize?

D: A bullet that is consistently retained by the far-side hide on a broadside shot through the shoulder probably exhibits terminal performance balanced between wound cavity volume and penetration. Time to death is expected to be relatively short, typified by an infrequent drop-to-the-shot or by more frequent, limited travel distance after the shot. The bullet is expected to perform well on full frontal and front quartering shots, but could be iffy on rear quartering ones. A bullet that consistently exits the far side-hide on a broadside shot through both shoulders or through the ribs likely exhibits terminal performance conceptually skewed toward penetration. The potential reduction in wound cavity volume could conceptually be expected to result in a longer time frame for death with associated longer travel distances. The blood trail is expected to be good. The bullet could also be expected to perform acceptably at any shot angle, including the rear quartering.

GG: Excellent summation. For what it’s worth, the African trackers I have watched are wired into another cosmos. Even if you give them less than a pencil eraser-head dollop of blood every ten yards or so, the odds are very good that they will find the animal.

I think we can now move on to what I believe are the terminal performance fog factors.

D: Fog factors?

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GG: Sidebar issues that can mask relevant terminal performance objectives associated with trophy hunting in Africa or might not be indicative of actual terminal performance. Any ideas?

D: The only one I’m sure of is meat damage. By definition, shots on the shoulder destroy edible meat. When we were talking about debilitating an animal, more blood-shot tissue on the shoulder is better. For trophy hunting, meat damage is a non-issue.

GG: Bingo. What about a bullet’s retained weight?

D: The more the better.

GG: My gel testing and Mann’s data indicate likely not.

“Geeze Louise,” thought Donny. “Here we go again! The Geezer wants to argue with what everybody knows is true.”

GG saw the Pilgrim’s obvious mental play of the BS card. He was expecting no less.

GG: Is there an appropriate single word that can be used to describe the material shed from a hunting bullet as it passes through the animal?

Donny was lost. But he damned-well knew one thing for sure: the bastard could read his mind. The Old Man’s facial expression told him he was going to be politely pilloried for his failure to keep an open mind.

D: I can’t think of any.

GG: How about shrapnel?

Donny stared at the Old Man. “Damn him.”

D: Like from a grenade or an artillery round?

GG: Yep.

D: Can I conclude that your gel testing showed that the material loss from the bullet contributed to generating the wound cavity?

GG: Yep. Mann’s data could also indicate the same trend. Quite simply, his data potentially indicate the greater the bullet weight loss, the greater the measured wound cavity volume.

D: But loss of weight means decreased momentum and thus decreased penetration.

GG: I believe it was you who used the word ‘effective’ in describing penetration. What can you potentially say about a bullet used for a broadside shot that lost 40% of its weight but was retained by the hide on the far-side shoulder?

Donny continued to stare at the Old Man. “Damn him.”

D: Well, a couple of things. First, the only reason you know the bullet lost 40% of its weight is because the animal was recovered. That means the bullet fulfilled its primary performance objective. Second, a skinning-shed autopsy would likely indicate a very good to excellent wound cavity. What would be interesting to know is whether the actual impact velocity was in the range considered by the manufacturer to be within the sweet-spot or in a recommended impact velocity range.

GG was impressed. A ‘sharpie’.

GG: Outstanding appraisal! In this example, what could you conclude if you determined the actual impact velocity was at the lower-bound impact velocity recommended by the manufacturer?

D: There could be a potentially serious penetration issue at the upper- bound recommended impact velocity.

GG: Excellent! Why?

D: A 40% weight loss at this lower-bound impact velocity could indicate the potential for the bullet to literally disintegrate or not reach the boiler room at the upper-bound impact velocity.

GG: Bingo! For the same example, what could you conclude if you determined that the actual impact velocity was at the upper bound recommended by the manufacturer?

D: The bullet was satisfactorily performing, maybe even within the manufacturer’s design intent. Certainly within the manufacturer’s expectation. The bullet could be expected to retain more weight at reduced impact velocities.

GG: Outstanding! What do you think about a bullet having a jacket-core separation?

D: I don’t know much, but I do know that’s considered the kiss of death as far as terminal performance goes. I suppose it all boils down to whether it affected the effective penetration. The only way folks would know if there was a jacket-core separation would be from an autopsy of a dead, and by definition, recovered animal. In that scenario, it’s kindly a non-issue because the penetration was obviously effective.

GG: Yep. Taylor summed it up best. The original intent of the copper jacket was to get lead out of the rifle barrel at a higher velocity and with less fouling than you could with just plain lead. One way to look at it is once the bullet leaves the bore, the jacket has done its job and really isn’t needed any more, kindly like a sabot. The jacket’s weight is miniscule compared to the lead’s weight, and it’s the lead that does the real work. I’ve had jacket-core separations in animals, but the separations have been at the termination length of the bullet. Same thing when I tested bullets with dry newspaper as the test medium.

I believe penetration is its own metric, solely related to impact velocity and the bullet’s generic design. If the penetration did the job, then the job was done. Trying to postulate what might-could-be’s without benefit of a manufacturer’s recommended impact velocity range or actual test data from multiple impact velocities is just plain mental masturbation. As far as I am concerned, so are the supposed effects of jacket-core separation.

What about a bullet’s mushroom diameter?

D: What did your testing indicate?

GG smiled. The Pilgrim had learned his lesson, at least temporarily.

GG: The mushroom diameter folks measure may not be the maximum. With some generic bullet designs, I think it likely is certainly within spittin’ distance. With some generic bullet designs, I think it likely isn’t.

Donny sat there trying to gin the ramifications of GG’s statement. GG could almost hear the gnashing of the mental gears as the youngun overloaded his mental synchros trying to engage.

D: Yeah. You mean like a grenade may have gone off and all we are doing is measuring the largest fragment?

Another belly laugh from GG, this time extending out for at least 5 seconds. Donny watched as the Old Man tried to compose himself.

GG: (Grinning like a Cheshire cat) Damned if you didn’t nuke that one ‘til it glowed!

I think folks believe the objective of measuring a bullet’s mushroom diameter is to indirectly assess how large a wound cavity was produced. The thinking is the larger the mushroom diameter, the better/larger/more substantial the wound cavity.

For some generic bullet designs, I think that is reasonable. As in your grenade response, I don’t think it is for others. If a bullet has shed an appreciable amount of weight, the weight loss is from the tip area. Somewhere within the animal or test media the mushroom may have blossomed to a diameter significantly greater than what we measure. The stress induced by passage of the bullet through the tissue/test media, particularly at a high impact velocity, may have potentially shaved down the tip to the ‘nub’ we see on the retained bullet.

Mann’s data indicate the wound cavity volume was increasing even though the recovered mushroom diameter decreased with increasing impact velocity, apparently due to an increase in penetration length. The decrease in mushroom diameter also generally coincided with the increase in weight loss, indicating the mushroom was being shaved down at higher impact velocities due to the higher drag stress. Even so, the wound cavity volume was increasing.

For me, there is no real substitute for a direct measurement of wound cavity volume. When that data are provided, weight retained and retained mushroom diameter become factoids.

D: And gel testing allows such a direct determination of wound cavity volume?

GG: The way I do it, yes.

D: How do you do it?