MASS MATTERS MOST


By The Outdoorsman & Warren Eastland
(An earlier version of this essay appears in Hunting & Safari Magazine)


The  issue  of what is the “best” caliber for any given hunting venue is a perennial topic of—sometimes heated—debate among hunters worldwide, at times taking on aspects of a religious controversy.  The central dogma of The Established Church of High Velocity (the main one in North America) is “Faster is better, and don’t you ever forget it!”  Most North American hunters are obsessed with velocity above all other qualities and tend to look with disfavor on mundane calibers throwing heavy bullets at medium speed. 

Such calibers are not sexy, nor have they  been sanctified by endless praise from writers (who of course are paid to sell the guns and ammunition advertised in their magazines).  Too, the American hunter has to be persuaded that he needs the latest UltraHyperMagnum.  Rifles last a long, long time, given anything approaching decent care: and if hunters were convinced that the .30-'06, .308, or .270 that they've had and used for decades were adequate, the rifle makers wouldn't have a market!


Our  observations in Africa and extensive discussions with PH's whose experience is vastly greater than ours  have convinced us that hunters who believe  that velocity is the most important factor in choice of caliber are doing a disservice to the game they hunt, and letting themselves in for trouble.  Most PHs we know have forcefully asserted that they wince when a foreign hunter arrives with a high-velocity, light-bullet Super-Duper Mangle-‘Em rifle. Pros guiding for plains game would much prefer to have a client bring a hum-drum, work-a-day .30-06 than anything else. They’ll tell you (if you ask) that for large animals,  penetration is what kills, and is by far the most important measure of performance.  A 7mm Super-Duper Mangle-‘Em that has eye-popping paper ballistics usually is not a good choice when someone makes that safari he’s saved up for over the years.


African antelope are mostly big critters, and they’re built tough.  Getting a bullet into one of them deeply enough to hit a vital structure is an absolute necessity to effect a clean kill.  Any caliber whose main selling point is bullet speed, not bullet mass, isn't going to be as effective as paper figures or prior experience in North America might lead someone to believe. 

The moose and bison are the only North American mammals that remotely compare to large African species in terms of body size and bone structure. The classic round for  both is the .45-70, hardly a speed demon: yet it wrought devastation among the huge herds of bison that once roamed the American west.


ENERGY

Looking through reference books, reading the backs of ammunition packages, and prominently displayed in the colorful sales brochures for various cartridges, you'll find velocity and its closely related derivative, kinetic energy (KE). The numbers, always in the thousands of foot-pounds, appear impressive. But far more important than kinetic energy in terms of effectiveness is the concept of momentum.  Momentum is what keeps the bullet moving in a  straight line after it encounters resistance, and only rarely is it included in ballistic tables. Momentum is what enables a bullet to get through the tough hide, the heavy muscles, and the dense bone structure of big animals to reach the vitals. 

Kinetic energy increases with the square of the velocity:

KE=MV(2)/2

so that a relatively moderate increase in speed produces a really large increase in paper energy. Note how only one-half the mass is used in KE calculations. But momentum is in direct proportion to both velocity and mass:

Mo= MV

Momentum is measured in foot-pounds-per-second (F-PS); the energy to move one pound a distance of one foot in one second. All else being equal, a heavy bullet has more momentum than a light one. A bullet may have lots of energy but if it lacks momentum it cannot effectively translate that energy into adequate penetration.


Consider the way a building is demolished: a wrecking ball is a prime example of how momentum matters. A wrecking ball weighing 3200 pounds and, moving at a very lazy velocity of 22 fps, has a substantial amount of kinetic energy, but what knocks out a square yard of solid masonry at a time isn't the theoretical energy of that ball, it's the actual momentum: in this example, 32,000 F-PS.  It takes a lot to stop something that heavy, even moving at a very slow speed. In our example, the momentum is sufficient to move a one-pound brick a distance of 32,000 feet, or move 16 tons of bricks a distance of one foot. It's going to make short work of that building. The same principle applies to a bullet.


A 540 grain bullet from a .505 Gibbs, about the largest caliber a normal human can fire from a rifle without injury, moves at 2300 fps. This is 100 times faster than the wrecking ball but it has only .000024% of the ball’s mass.  It has a whopping amount of kinetic energy but its momentum is only 177.4 F-PS.  While the Gibbs is adequate for any animal on this planet, it would be take a very, very long time to knock down a building by shooting one at it. If we extrapolate from this admittedly extreme example, we have to conclude that hunting calibers for big animals need high levels of momentum, and that kinetic energy is a secondary consideration in caliber selection. 


Nothing illustrates this principle better than the use of the .270 Winchester with 130 grain bullets on African game. Many Americans who own and dearly love their .270's bring them to Africa and use them with a fair degree of success: and while there probably isn't any hard data on the rate of animals lost with this caliber compared to others, our own experience has persuaded us that the standard 130 grain bullet is marginal at best

Nobody questions that the .270 is an outstanding round for medium-sized animals: but it's too light for big stuff, and in Africa nearly everything qualifies as big stuff.  In Africa the .270 with standard ammunition is a gun for experts, because its killing effectiveness depends on perfect bullet placement. As we all know, perfect placement isn't always achieved, especially not by an excited hunter on a once-in-a-lifetime safari.


The .30-06, a caliber whose performance on plains game has been proven over many, many years of use, can be used as a yardstick. A 180 grain bullet at 2700 fps has a momentum  of 69.4 F-PS (bullet weight, used as a substitute for mass, has to be corrected to pounds by being divided by 7000 before being used in the formulae for KE and momentum); a 200-grain bullet has momentum of 75 F-PS.  The 130-grain bullet of the .270 Winchester at 3140 fps has a paper energy of 2847 FP. But its momentum is only 58.3 F-PS. 

Even the dull-as-ditchwater 8x57, whose praises Jack O'Connor never sang, with its 196-grain bullet moving 600 fps slower than that .270, has a momentum figure  of 77.8 F-PS, better even than our "yardstick" 180-grain .30-06.   The very much higher velocity of the .270's light bullet gives it no momentous advantage over the .30-06 or the plodding 8x57's heavy one.


MASS

Repeat: it’s not theoretical energy that matters most, it’s the tendency of the bullet to resist deflection, and that is a function of the bullet's mass.  Heavily constructed bullets with high momentum penetrate deeply to reach important structures.

Well, OK, the .270 can be had with heavier bullets. What happens then? The heaviest bullet available for the .270 is 156 grains at 2854 fps. This load has a momentum of  63.6 F-PS, 5.8 F-PS less than our yardstick round of an 180 grain  .30-06, and nearly 20 F-PS less than the 8x57.  

In short, however stellar a performer a .270 is with 130 grain bullets on lightly built animals, that 11.1 F-PS difference from our yardstick round makes it less likely to make one-shot kill on a blue wildebeest  (let alone something bigger) without absolutely perfect placement.


THE BULLET ITSELF

Then there is the matter of the bullets themselves.  To achieve high muzzle velocity lightweight bullets have to be used. Compare the .270 using the 130-grain bullet (3140 fps) and the 156-grain bullet (2854 fps). The heavier bullet has the higher momentum despite moving some 300 fps slower; that's the difference between theoretical energy and the actual energy available to do work – kill the animal. But it's still  below the .30-06 or the 8x57. Furthermore, that 130 grain bullet has a much lower sectional density (SD, the ratio of weight to cross sectional diameter).

High SD translates to higher momentum and retained energy down range. Lightweight fast bullets don't have enough SD to retain velocity over long distances, i.e., their momentum is low.

Furthermore,  all bullets yaw to some extent when encountering a change in medium, i.e., air to animal tissue.  Since animals aren't uniform in composition the presence of bone, ligaments, and tendons affects the path the bullet will take once it enters the body.   The lower sectional density of a light bullet  means it will almost certainly veer more on encountering  resistance than a heavier one would; while you might have been aiming at the heart, the inability of the bullet to stay on on track means that you might not hit it.


Of course it's theoretically possible to make a bullet of any desired weight in any desired diameter: but then there are issues with stabilization, not to mention materials. Sporting calibers use long-established "standard" twist rates that will stabilize bullets falling within a reasonably generous range of weights (and hence SD's). If you make the bullet very long (and hence heavy) to maintain SD, stability suffers because the twist rate (based on bullet diameter and length using the “Greenhill Formula”) is insufficient to stabilize the bullet. The Greenhill Formula is based on the length of the bullet, and the longer the bullet the faster it has to spin to be stable. Beyond a certain length, standard rifling twists can't spin it fast enough.


There's no way out of this trap without building a custom rifle having a custom rate of twist, which is not only a very expensive proposition but a fruitless quest. High velocity requires light bullets in barrel with standard twist rates; rifles with normal twist rates. Increase the weight (which increases the length) and retain the diameter, and accuracy goes over the side because the bullet is not stable in flight. Speed up the twist for the long, heavy bullet, and the abrupt entry into the rifling will damage the jacket material, also destroying accuracy in the process.


BULLET CONSTRUCTION

Light weight goes hand in hand with fragile construction. Remember: to achieve high velocity one must use light bullets. Pushing the bullet too fast often causes lightweight projectiles to break up on impact. If you toughen the jacket to resist break-up, you get lower sectional density for the same length—because copper weighs less than lead.  Lower sectional density is exactly the opposite of what’s needed.

A fast-moving conventional cup-and-core bullet that encounters the heavy bones typical of a large animal will be prone to breaking up on impact, failing to achieve the deep penetration needed to reach vital organs.  Striking  the humerus or scapula of a heavily-built animal will frequently cause break-up , achieving at best a relatively shallow wound. What a light bullet is  not likely to do is penetrate those bones in a straight line, entering the chest and striking the heart and lungs behind them. That's what high SD and high momentum allow a properly-designed bullet to do.

We've seen this happen more than once.   Anything heavier than an  impala shot with a  .270 using a lightweight bullet often requires a second shot,  even with near-perfect bullet placement.  One-shot kills, even on medium sized animals such as blesbok and hartebeest,  are less likely using light, fast bullets.   One of us has a safari partner who lost a magnificent kudu using  a .270 with 130-grain bullets. Oh, he hit the animal, and it eventually died, but the bullet entered the tough musculature of the brisket, blowing a superficial hole without penetrating the chest cavity, something that would almost certainly not have happened had he used heavier bullets. He paid for that kudu, and the kudu paid dearly for his choice, taking several days to die. He eventually killed another kudu with his .270 and required a finishing shot on that one, too.


On the other hand, Warren and his wife Wini have taken a couple of kudu, a half-dozen impala, a couple of gemsbok, a blesbok, a nyala, a warthog, a bushbuck, a couple of zebra, and smaller antelope, all with one shot kills from a .270 using 150 grain bullets.  This would argue that one shot kills are a function of the shooter and a good bullet.

A very heavy, well-constructed bullet, penetrates astonishingly well. The fired bullet in the image at left is a Hornady "Dangerous Game" full-metal-jacket from a .416 Remington. It was recovered from the skull of an elephant. It was the "insurance shot," fired into the back of the neck. This bullet traveled more than three feet through solid bone and muscle, coming to rest in the tongue of the beast: it was found during the butchering process. It is virtually undeformed, and probably could be loaded and fired again. That's penetration.


LOCATION, LOCATION, LOCATION

Shot placement is without doubt the key to success no matter what you shoot or are shooting at. Even a fast-stepping Super-Duper Mangle’Em will invariably give good results if the bullet is placed where it won’t encounter heavy bone structure: between the ribs, for example. But even the rib bones of most African antelope are sufficiently stout that light bullets will break up or be deflected off a straight line.  A poorly placed shot is poorly placed, whether it be from a .505 Gibbs or a .270 Winchester. The difference between the two poorly placed shots is that the larger diameter of the .505 will create a larger wound channel and put an animal in extremis faster than the narrow wound channel from a .270.

Too often, the lighter recoil of the .270 is its justification for use.  Flinching with large calibers used by inexperienced shooters causes poorly placed shots.  Whether the extra tracking involved from shooters who flinch is greater than the tracking involved from a less-than-quick kill from a smaller caliber that doesn't penetrate well is unknown, and perhaps, unknowable.


BIGGER IS BETTER

Much of the advantage of the larger calibers is in their use of what might be termed a “pre-expanded” bullet.  A .270 has to expand to nearly half-again its original diameter just to equal the entry size of the .375 bullet.  And think about the path; the .375 starts at entry with its large diameter while the .270 doesn't achieve the .375's unexpanded diameter until it is already deep in the body, perhaps past the vitals and on the way out.

Most African PH's don't like "boiler room" shots, the ones American hunters are trained to make: a hit behind the shoulder into the lung and heart area. The PH will usually advise a client to aim for the shoulder: "Come up the leg to one-third of the body depth, that's where the heart is and that's where your bullet should go."  The fine book The Perfect Shot, by Dr Kevin Robertson always recommends the heart/shoulder shot as the most reliable one and so does every PH we know. As Elmer Keith remarked, "The role of the bullet is to make two holes: one lets the air in and the other lets the blood out." Regardless of caliber, a heavy bullet is far, far more likely to achieve the through-and-through penetration this describes than a light one.

There is no doubt that a two-lung hit is fatal but can mean a very long tracking job, because the animal often can run amazing distances on sheer adrenalin. Furthermore, with light bullets there is no guarantee of a two-lung hit, especially if the bullet is deflected by a rib. An antelope with one functioning lung left can run for miles, often without leaving a decent blood trail. And it may well survive the hit. A hit in the shoulder joint is far more likely to knock the animal down, immobilizing it until the hunter can put in a second round to finish the job.

Most plains game hunting by North American hunters now takes place in South Africa for a myriad reasons, and a sad truth is that the trackers of modern South Africa rarely have the ability of their forebears. The near-certainty that the PH's trackers would find a wounded animal, something assumed just a few decades ago, is no longer there.


A client pays for blood drawn; no PH likes to charge a client a hefty trophy fee for an animal wounded and lost.  It's incumbent on the hunter who wants to make a quick, clean, ethical kill to follow Robert Ruark's sage advice: "Use enough gun."


THE SOLUTION

The answer to the hunter's dilemma in Africa is—may  we have the envelope please?—heavy, toughly constructed bullets at moderate velocities. More than a century and a half of regular use in Africa has shown beyond doubt that adequately stabilized, heavy-for-caliber bullets (i.e., those with high sectional density and high momentum) moving at moderate speeds kill far better than their paper ballistics might predict to be the case. 

In the past, the .303 using a 215-grain bullet found great favor with individuals hunting really big stuff, like elephant. (Yes, elephant. No one in his senses would hunt elephant nowadays with a .303, but it has been done, and not just by Karamojo Bell in the 19th Century. Even today elephant are still taken with .303's by those who have no other rifle.)

Momentum, momentum, momentum. That's what makes a rifle work. Most PH's will carry something like a .375 H&H or a .416 as a working rifle. Some will use the .300 Winchester Magnum as a "ranch rifle," but you will be hard pressed to find any one of them using a .270 as his all-around gun.


To return specifically to the .270: in  our opinion and experience it’s marginal at best using standard 130 grain bullets, when considered as an all-around caliber in Africa.  It will give sterling service on warthog or impala or springbok, and in the hands of an expert and a cool, calm shot—adjectives that usually don't apply to visitors on a once-in-a-lifetime safari—it will kill bigger animals, but all too often not outright. It almost always requires a follow-up on such creatures as wildebeest. Only a madman would use a .270 on a Cape buffalo, and it likely wouldn't penetrate the inch-and-a-half-thick hide of an old bull giraffe. As a plains game round for animals kudu sized and smaller, using 150 grain bullets, it is sufficient in the hands of a calm, experienced straight shooter.


It will be asked why the 7x57 (also known in Africa as the .275 Rigby) which fires a bullet of near-identical size to the .270, has a good reputation on African game, despite paper ballistics somewhat "inferior" to the .270's and a momentum figure no better. The answer to this riddle is simple: the 7x57 isn't a high-velocity round, and its bullet doesn't break up on impact. It remains intact and penetrates to the vitals. A heavy and tough bullet in the .270 would work just as well, but that would of course negate the supposed "advantage" the .270 has in its high velocity and paper energies with the 130 grain bullet.

With the heavier bullets, the .270 and the .275 Rigby are comparable in performance.  But remember that 7X57 ammo is available with 175 grain bullets and their superior SD. (Karamojo Bell, often held up as the epitome of the small caliber aficionados, used 7x57 ammo from DWM, because the British-made Kynoch ammunition of his day fired a light bullet that simply didn't penetrate as well as the heavier, slower, DWM bullets. And while everyone knows that Bell killed a lot of elephants with the 7x57, we are never told how many he lost.)

Similarly, the 7mm Magnum, beloved of so many shooters and hunters in western North America, moves its bullets too fast. If one were to use heavily-constructed, more massive, bullets in this caliber it would work...but again, the "advantage" of the high velocity would be lost.

The argument is often made that the trajectory of high-velocity bullets is flatter and therefore they require less holdover at long range. This is true, but most African game is shot at much shorter ranges than it is in, say, Saskatchewan or Colorado. At 100 or even 200 yards the slower bullets are at no real disadvantage, and the much faster ones have a greater tendency to disintegrate before penetrating deeply enough to get to the vitals.


Another drawback to high-velocity bullets is their tendency to damage meat. Foreigners hunt Africa for trophies, but the landowner who owns the game and expects to sell the meat for a profit isn’t happy with large bloodshot chunks, nor are local hunters who want biltong.  During a safari in Namibia, an incident that nicely illustrates this point occurred.  One of us had a hunting partner whose son had come along and was  using a rifle chambered for the .300 Remington Ultra Mag.  His father, with a good deal of African hunting experience, used a .416 Remington. The .300 used 200 grain bullets at 3032 FPSfps, the .416 a 400-grain bullet at a comparatively plodding 2400 FPSfps. The momentum for the .300 RUM bullet is  86.6 F-PS; for the .416 it is 137 F-PS.

The son shot a very large kudu bull in the neck.  The father shot a zebra of comparable size in the same place.  Both animals were were killed with one shot, at comparable ranges of 40 yards or so. In both cases the bullet passed completely through. The entry wound from the .300 RUM showed significant amounts of bloodshot meat; the exit wound on the underside of the neck was simply a jelly-like mass with extensive areas of damage.  By comparison, the entry wound from the .416 was barely visible, and the exit wound not much larger.


PREMIUM BULLETS

Some of the deficiencies (but not all) of small diameter, high velocity calibers can be overcome by the use of premium bullets.  Much of the foregoing discussion has been based on observations  using standard cup-and-core bullets. It's true that vastly better bullets are available to hunters today that those of even 25 years ago, regardless of the game or hunting venue. 

But one thing to remember about KE is that it acts on the bullet as well as on the animal the bullet strikes.  Animal tissue is resilient, negating much of KE's effects, but bullets aren't. Up the KE and you up the stress on the bullet. Premium bullets, especially those with bonded cores (like the Swift A-frame) withstand the deforming effects of KE better than standard cup-and-core bullets, but the lighter weight ones still have a low Sectional Density. 

Upon impact, the length of the bullet in relationship to its diameter is immediately reduced, limiting its penetration depth and increasing the deviation from the bullet's intended path. Indeed, looking at the .270 Winchester, even with 150 grain premium bullets, the momentum is a bit over 61 F-PS, less than 8 F-PS lower than our yardstick round. The bullet won't break up, but neither will it penetrate as deeply as one could wish.


AFRICAN CALIBERS

It is a historical fact that the African continent was first colonized by people using muzzle-loading rifles firing large projectiles at low velocity; and later "conquered" by people using the .577 Snider, .450 Martini-Henry, .303 British, 7x57 Mauser, and 8x57 Mauser. With a few notable exceptions, the hunter-explorers equipped themselves with rifles in those calibers for plains game, and used them if needed for larger animals, though with discretion. Even today, many a farm manger has a .303 as his "light rifle" and the caliber is widely used across sub-Saharan Africa for game at bushveld ranges. The great 19th and early 20th Century gun makers—Rigby, H&H, Mauser, Westley Richards, and many less-well-known companies—all had a steady trade supplying rifles to settlers and explorers in these and similar calibers. Large caliber double rifles (e.g., .500, .500-450, and similar metric equivalents) were also offered to sport hunters, first in black powder and later in smokeless versions.

Of course to a large extent the medium-bore plains game calibers so widely used by farmers and ranchers were chosen because of the ready availability of military ammunition, a consideration that didn't apply to well-heeled foreign hunters like Theodore Roosevelt (who used an H&H double rifle in .500/.450) but this is not entirely true. The plain fact is that these calibers worked, and worked well in Africa. They still do.