Book Chapter 21-Home

Hunting Bullet Metrics

Apply Terminal Performance Truth

AFRICA HUNTER QUEST©

Chapter 21 - THE PILGRIM’S CHAMBERING AND BULLET

Donny stared at the blank piece of paper, his calculator, a pencil, and an eraser at the ready. He recognized he had taken a good cut at what GG had described as the first level of his hunting problem definition. He was now ready to consider the issues at the second level, the one he dreaded. He knew he had to make firm terminal performance decisions that would affect his hunting problem definition’s final outcome and determine his hunt strategies.

The fact that he was even considering any numbers-based analysis confounded him. He truly didn’t like self-absorbed, sanctimonious nerds who supposedly defined reality with number surety to the fourth decimal place. They had no apparent regard for the universal truth that ‘$#!+ happens’. He did not want to be considered one of ‘them’.

Donny contemplated the evenly spaced lines on the paper. The spaces implied some ranking that needed filled in; the lines suggested some logic linearity to that process. But wasn’t that conceptually what he had just done as he evolved defining the first-level issues of his hunting definition? Only now he felt like there was no wiggle room, no operating outside the lines. Numbers would govern and control his decision-making process. It made him uneasy. He intrinsically knew decisions must be made with limited to no benefit of personal experience.

What did he know for sure? First, his 130-grainer wouldn’t cut it. Period. The impact velocity was too high for a cup and core bullet on shoulder shots at 165 yards. Second, Robertson indicated the 270 Winchester with a 150-grain bullet was lower bound to marginal for kudu, gemsbok, and zebra. The four PHs in Harrisburg never mentioned a 270 Winchester as the preferred chambering for kudu. When he asked about a 270 Winchester, the PC responses bordered on pandering. Regardless of what his dad and GG thought about his 270 Winchester, the local experts were not keen on its use.

“Hmmmm,” thought Donny. “The only good news thus far is I have avoided a potential disaster by not even considering my 130-grain ammo. The bad news is all the locals would think that me showing up with a 150-grain ammo would be like showing up with a garden hose at a house fire. It might work for a little fire, but I could expect complete toast with a big one. “

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But he had found a clue that led him to believe he could potentially use his 270 Winchester: a manufacturer produced a 180-grain bonded-lead core bullet with a stated, recommended impact velocity range of 2000 to 3000 fps. This bullet weight was actually heavier than the 7-mag, 175-grainer recommended by the PH from the Orange Free State. The only difference was the chambering: his would be a 270 Winchester compared to a 7-mm magnum. The difference in caliber was only 0.007 inches, so small that it could be considered negligible, even in an expanded mushroom end area comparison.

Donny reluctantly allowed himself to be funneled to GG’s empiricism. What was the estimated game weight for a 175-grainer launched from a 7-mm Remington mag for both 165 and 330 yards? How did that compare to the likely weight of a trophy kudu? If the empiricism was close to predicting the weight of a trophy kudu, what weight would it predict for a 180-grainer from his 270 Winchester at those distances? And just how marginal would a 150-grainer be? “Easy enough to figure out,” thought Donny.

Donny first went online for specs on 7-mag ammo with 175-grain bullets. He found two: one with a cup and core bullet with a BC of .427 and a muzzle velocity of 2860 fps, the other with a dual-lead cell bullet with an unbonded front cell. The ammo had a specified bullet BC of .519 and a muzzle velocity of 2800 fps. He noted that the cup and core bullet might work because its impact velocity at 165 yards was likely going to be less than 2700 fps. Donny first decided to enter the 175-grain cup and core data into his selected ballistic software to find out.

Donny went online and accessed the ballistic program. For the first time he critically eyed the input parameters because this evaluation was well beyond ‘down and dirty’. Although he knew he was going to plug the computed velocities into an empiricism that he didn’t trust, he still wanted to reflect as much hunting reality as he could.

Donny focused on the environmental factors, as he had no realistic data to plug in. He went online to identify likely altitude, temperature, pressure, humidity, and wind velocity values in the Orange Free State in June. He was surprised at the potential for high sustained winds, particularly when a front passed through. He settled on what he believed were representative values, glad that he had taken the time to research those conditions.

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Donny plugged in all the data and studied the output for the cup and core 175-grainer. He had been right: the impact velocity at 165 yards was about 2550 fps, well below GG’s 2700 fps threshold for a broadside shoulder shot. The impact velocity at 330 yards was about 2240 fps, well above what GG had said was Nathan Foster’s lower-bound value of 1800 fps. Donny concluded a cup and core bullet would have impact velocities likely compatible with its generic design within the typical shot distances identified by the Orange Free State PH. Based on his conversations with GG, the bullet could be expected to produce terminal performance with a likely balance between wound cavity formation and penetration within that range of impact velocities.

“Now,” thought Donny. “The acid test.” He took the estimated impact velocity of 2240 fps at 330 yards and plugged it into GG’s empiricism. The resulting value was an estimated plains game weight of 510 pounds. “Dang!” thought Donny. “That’s within spittin’ distance of a trophy kudu bull weight! It’s so close to 540 pounds that it’s scary. I would have never believed it.”

Donny sat back and considered the implications of his calculation. The marquee conclusion was a bullet weighing 175 grains essentially got the job done at the maximum expected shot distance of 330 yards. Even fired from a kick-a$$ chambering like a 7-mag, a simple cup and core bullet would work, and likely work well. The potential for a 180-grainer launched from his 270 Winchester actually working grew exponentially.

“Do I really need a 180-grain bullet?” thought Donny. “I really don’t want to hand-load ammo. How would a high BC 150-grainer launched from off-the-shelf ammo potentially do?”

Donny went back online and identified a bonded-lead cell 150-grainer with a polymer tip. The published BC of the bullet was .591. The manufacturer claimed a muzzle velocity of 2850 fps.

Donny again accessed his online ballistic software and plugged in the BC and muzzle velocity. The output identified an impact velocity of 2400 fps at 330 yards. A quick calculation of estimated game weight from GG’s empiricism yielded a little over 400 pounds.

“Not even close,” thought Donny. He fought back the urge to play the BS card and totally shut down the evaluation path he had begun. What did that deficient weight calculation actually mean? “Depends on the measuring stick,” he thought.

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He recalled GG’s comment about using the empiricism as a pass-fail indicator. If he used it that way, the 150-grainer would absolutely not work. Period. Yet when he used it to estimate the game weight from a 175-grainer and had come up a tad shy, he had concluded the bullet weight was close enough. He realized he had used the empiricism as a relative-risk indicator and had immediately arrived at the conclusion a 175-grainer would be satisfactory because there was no appreciable increase in risk of losing an animal. For his 270 Winchester, it now became clear that he was better off using GG’s empiricism as a relative-risk indicator rather than a pass-fail indicator.

If the empiricism was even reasonably accurate, using a 150-grain bullet resulted in a 140-pound bust between what he needed at 330 yards and the likely weight of a prime kudu bull. How to compensate for that bust using a 150-grainer?

“Reduce the shot distance so I can damn-well hit the heart,” thought Donny. He didn’t know what that distance limitation should reasonably be because he didn’t know the accuracy of that 150-grain ammo through his rifle. He now realized that the Old Man’s obsession with accuracy was no longer anality run amuck. Accuracy that was good enough for the lungs at 50 yards from any shooting position could be problematic for the heart at 330 yards, even if shot prone off a bipod. Not only that, the distance would be further reduced if he had to use sticks instead of a bipod, seated or otherwise.

But the urge to play the BS card finally overwhelmed Donny. “Yeah, yeah, yeah, BS! A .277-cal bullet is a .277 bullet, no matter if it is 90 grains or 180 grains. A 150-grainer into the lungs will put a trophy kudu mount on the wall. It’s as simple as that.”

Donny was in the process of thinking “We don’t need no stinkin’ numbers” when the reality implications started to creep in. He was risking a $2,500 trophy fee. That was a number that definitely would stink up the experience if he somehow didn’t recover the kudu. The risk would be lower if the 150-grainer completely perforated the animal for a good blood trail. Would it? He had no test data nor stated recommendations for impact velocities. The manufacturer of the 150-grainer only furnished pictures of deformed bullets. As it turned out, one of the pictures was of a bullet that had a stated impact velocity of 2400 fps, the same as what he could expect from his maximum anticipated shot. What was this test bullet’s caliber? How far had it penetrated into the test medium and just what was the test medium? “Dang if I ain’t soundin’ like the Geezer,” thought Donny. “Maybe I need to retract my BS

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card.” He ruefully had to admit that he had just been a prime target for a boomer like GG to tell him to take a chill pill.

Regardless of GG’s empiricism, both Taylor and Robertson indicated bullet weight was important. Greater weight invariably meant greater momentum. Greater weight invariably meant greater punch, no matter how folks chose to define it. More punch meant the potential for more debilitation. For the same caliber and generic design, more momentum could potentially translate into greater penetration. GG’s empiricism had merely underscored the importance of bullet weight.

Donny didn’t want anything to do with reloading his own ammo. He knew he had instinctively pushed back for that very reason when he saw the disparity between the estimated game weight indicated by GG’s empiricism when a 150-grainer was used and the weight of a trophy kudu. Even more unpleasant was the prospect of borrowing a different rifle or having his current rifle fitted with a different barrel and attendant chambering.

Since he judged reloading to be the least of those alternative ‘evils’, he decided to check if a 180-grainer could potentially work out of his 270 Winchester. If it did, he could decide if the potential risk of losing an animal by shooting a 150-grainer was worth the aggravation of reloading for a 180-grainer.

Donny again went online searching for load development data on the 180-grainer. What he expected to be a saga turned out stunningly simple: he found a manufacturer that sold his selected 180-grainer in off-the-shelf ammo! No reloading!!

The manufacturer referenced a muzzle velocity of 2625 fps from a 24-inch barrel and 2550 from a 22-inch barrel. Donny did a quick calculation and determined that the load gained about 35 fps for each inch increase in barrel length. He had a 26-inch barrel, so he figured he might have a muzzle velocity of about 2700 fps available. Manufacturers were notorious for overstating muzzle velocity, so he rounded it down to 2650 fps.

Donny again accessed his online ballistic software. He plugged in the manufacturer’s claimed BC of .513 and a muzzle velocity of 2650 fps. The resultant impact velocity at 330 yards was about 2150 fps. A quick calculation with GG’s empiricism yielded an estimated game weight of about 520 pounds. “I hate soundin’ like the Old Man,” thought Donny, “but damned if that ain’t BINGO!”

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After the euphoria of the 520 pounds died away, Donny contemplated the estimated impact velocity of 2150 fps. It was well above the manufacturer’s lower bound of 2000 fps, but quite a bit below GG’s arbitrary lower bound of 2400 fps. Was that a discrepancy of any consequence?

Donny really didn’t know. His 2150 fps estimate was well above the manufacturer’s lower bound, and he thus considered it golden. The bullet ought to work just fine in terms of terminal performance. But what was the terminal performance?

Donny then remembered that GG’s 2400 fps lower bound was based on Nathan Foster’s observation that the terminal performance of bonded-lead core bullets seemed to fall off below that impact velocity. GG had interpreted that to mean the bullets were not mushrooming as significantly below that velocity and thus there was a resultant falloff of wound cavity volume. GG was a drop-at-the-shot freak and believed that a greater wound cavity volume decreased the time for death. Was that an issue for his application?

“Probably not,” thought Donny. In his particular case, he was nearing the lower bound of the recommended impact velocity range. If that impact velocity range was a sweet-spot range, that implied potentially somewhat less penetration compared to penetration that might be available at the upper bound impact velocity. If the manufacturer’s recommended impact velocity range was not a sweet-spot range, the decrease in mushroom diameter at a lower impact velocity could potentially imply an increase in the bullet’s ability to penetrate with attendant less wound cavity formation. “I may or may not have enough penetration for a ‘perforate to ventilate’ scenario. But if I get into the boiler room in general and the heart in particular, the manufacturer has indicated that the terminal performance of this bullet should be satisfactory.”

Donny expected the animals to travel at least 200 yards after the shot, likely more, because of potentially reduced wound cavities produced from his predicted impact velocity at 330 yards. Even though he could not be sure of either the terrain or the vegetation in the Orange Free State, he could be sure that the tracking expertise available would likely be well beyond his, potentially approaching cosmic in proficiency. He assessed if he did his job as a marksman, the risk of an unrecovered animal was relatively small.

The accuracy of this loaded 180-grain ammo was not known. “I may have to limit my shot distance off of sticks or rely on use of a bipod from the seated position to be

sure of taking out the heart at a distance potentially considerably less than 330 yards,” thought Donnie. “I need to revisit this issue once I know what my actual accuracy is.”

What about a shot at 165 yards? Donny eyed the output on his screen and picked out about 2400 fps at 160 yards. With a likely upper impact velocity of 2400 fps, it looked as though the 180-grainer could potentially still be more of a penetrator than an expander. However, there would likely be an appreciable increase in wound cavity volume compared to what could be expected at 2150 fps. As such, animal travel distance after the shot could theoretically be less, but maybe not to any appreciable extent. He could certainly live with the likely expected terminal performance at 165 yards, again given the likely tracking expertise that would be available.

Donny sat back, almost giddy from the unexpected success of finding off-the-shelf ammo loaded with the 180-grain bonded-lead core bullet that had just conceptually passed terminal performance muster. Icing to that cake was actually having estimated game-weight numbers GG claimed were conservative that supported its potentially successful use. He had forced himself to focus on GG’s sometimes pedantic spews and was amazed at how much he had retained. GG’s seemingly inconsequential and superfluous factoids had been relevant in critically assessing the 180’s ammo performance. He had persevered and been the sponge.

He was in the process of shutting down his computer when he had an “Oh $#!+” moment: what about the other animals?

Donny went back to his list of animals and estimated weights and quickly determined that all the animals except the zebra fell comfortably within the estimated game-weight capacity of his 180-grainer, even at 330 yards. But at 165 yards, he estimated the game weight was about 580 pounds, potentially about 50 pounds shy of a trophy-grade zebra. At 330 yards, the estimated game weight was about 525 pounds, or about 100 pounds shy.

Donny assessed that this probably wouldn’t be of any major concern, particularly if he limited his shots to the heart from a broadside or a front quartering only. The actual ammo accuracy and method of rifle support would be key to evaluating and identifying a potential maximum shot distance based on taking out the heart. He would simply make a field assessment based on the conditions he found during his zebra hunt and any accumulated performance data he had acquired from his 180-grainer.

Donny continued to gaze at his computer screen. His revelation about needing to check the other animals and their weights had rattled him. He had been too quick to take his gift, pull the plug, and run. He sensed another issue was pin-balling around in his subconscious that needed focus. What?!

Donny fixated on the impact velocities tabulated on the screen. All less than 2700 fps. 2400 fps at 160 yards. 2150 fps at 330 yards……..”Holy $#!+!!!!” thought Donny. “Impact velocities are in a cup and core’s wheelhouse! A 180-grainer in .277-caliber is classic Africa big and slow!!!”

“I never consciously decided what I wanted as far as bullet terminal performance,” thought Donny. “I only had one bullet choice available in a weight considered satisfactory. Its generic design indicated likely terminal performance balanced between wound cavity volume and penetration, but probably only if I drove it fast enough to achieve impact velocities above 2400 fps. With the reduced impact velocities from my 270 Winchester, I judged the 180-grainer’s terminal performance would be skewed more to penetration than a balance between wound cavity formation and penetration based more on what a practitioner has to say than the uncommon, hard recommendation from the manufacturer. I rationalized such performance would be low risk in terms of a lost animal given the tracker expertise that would likely be available and the fact that the manufacturer believed that the bullet’s net terminal performance would be satisfactory.

A 180-grain cup and core bullet would likely produce terminal performance balanced between wound cavity volume and penetration within the actual impact velocity range associated with my shot distances. Such balanced performance could potentially reduce travel distance after the shot. Regardless of travel distance after the shot, the inferred odds of losing an animal with either bullet are judged to be acceptably low. If a cup and core 180-grainer had been available, which one would have I selected?”

“Damned if I know,” thought Donny. GG’s direct and implied assertions that ‘Africa is different’ potentially indicated the terminal performance measuring sticks he used for taking white tails at the farm may not be directly applicable for taking the game he intended to hunt in Africa. The 180-grain bonded-lead core’s likely ‘penetrator’ performance was probably in keeping with his natural inclination to preserve meat. Was that inclination relevant in terms of trophy hunting Africa plains game? “Skinning-shed autopsies and soliciting opinions from my PH about the 180

-grainer’s performance should be considered mandatory to resolve this issue,” thought Donny.

Donny shut down the ballistic program. He pushed back from his computer and contemplated what he had just accomplished. He had been shown resources, had learned terminal performance concepts, and had used a wildcat analytical tool to critically evaluate terminal performance issues on his own terms. He had defined his unique hunting problem and crafted a plan that would enable him to make reasonably informed decisions that considerably reduced the odds of a lost animal. He now felt confident that his 270 Winchester and 180-grainer ammo combination was a reasonably good tool for harvesting the animals on his bag list. If he followed GG’s advice about practicing with his rifle, he was well on his way to reducing the prospect of ‘$#!+ happens’.