Which Calibre to Choose?
By Gregor Woods
Editor: Hunting & Rifles, Magnum Magazine
This subject really needs a more comprehensive discussion than website space permits. Here I can but touch on some of the most important principles. The question, “Which calibre to choose” cannot be answered in general terms as there are too many variables. Talk of one calibre being “better” than another is meaningless. Better for whom? Better for what game category? Better for what hunting conditions? There is no simple answer – “terms and conditions apply”.
We must begin by asserting that there are other factors in the equation that are equally or more important than calibre choice, for example correct shot placement – without which no cartridge can be suitably effective. Likewise, if the mechanical construction of the bullet (projectile) is not adequate to the task of reaching and effectively destroying the vital organs (irrespective of what bones it may encounter en route) calibre choice means little.
Not all bullets are equal – far from it. Ideally, an expanding bullet must “mushroom” in a controlled manner, so that it achieves its maximum diameter as it passes through the vital organs – irrespective of the volume of tissue and bone through which it must travel en route to the vital organs. The very latest, greatest “wonder cartridge” is worthless if the bullet used is too fragile to withstand its own high impact velocity, hence breaks up in the animal, failing to reach the vital organs. So there is more to it than “choosing a calibre”.
If you use a bullet whose mechanical construction is appropriate to the task on hand, and you put it in the right place (and at the correct angle to align it with the vital organs within the animal), then choice of calibre becomes far less important than you may imagine. Even on a large antelope like a kudu bull or a blue wildebeest, if the animal is standing broadside (“plankdwars”) so that you can place the bullet centrally in the “vital triangle” of the shoulder (meaning it will encounter no bone heavier than a rib on its way to the heart/lungs) and the range is within, say 150 metres, then it does not really make any difference whether you have chosen a 7×57 or a .30-06 or a .375H&H. Naturally, this also assumes that your bullet is heavy enough to provide the momentum needed to reach the vitals.
Right, having said all that, some calibres are certainly more appropriate than others for use on animals in various weight classes and in differing terrain types. But instead of thinking in terms of “choosing a calibre”, rather approach it in terms of matching ballistics to game and conditions. Obviously, large, heavily-boned animals like kudu bulls or wildebeest require bigger, heavier, stronger bullets than smaller, lightweight animals such as springbuck. By the same token, terrain conditions which call for longer shots (e.g. flat, open plains) require bullets travelling at higher velocities to provide a flatter trajectory (this makes precise judging of distance less important, thus eliminating or reducing the need to allow for “bullet drop” when aiming). The .300 Win Mag, for example, using strongly constructed 220gr bullets, is suitable for kudu in bushveld conditions, while that very same cartridge using 165gr bullets (of practically any construction) can be used for hunting springbuck at long range on the desert plains. Practically any calibre can be made more effective by adjusting its ballistics to match the particular game and conditions.
Simply put, “ballistics” refers to the diameter, weight, shape and construction of the projectile, in conjunction with its velocity. These factors determine the trajectory of the bullet, its ability to resist wind deflection, its striking energy, its momentum, and its performance after impact (i.e. the degree and rapidity of its expansion, its weight retention and penetration potential). Bear in mind that, all else being equal, distance influences impact velocity. A bullet striking an animal only 80 metres from the shooter, will still be travelling at almost the same velocity as when it exited the muzzle. Fire the very same calibre/bullet/load combination at an animal 300 metres away, and the projectile has time to slow down prior to impact. At high impact velocities, lightweight, fragile bullets tend to expand too rapidly or disintegrate in the animal, thus should not be used on large animals at close to moderate range. At 300 metres, however, the very same bullets (which left the muzzle at the very same velocity) have slowed down enough to expand normally, hold together and retain enough weight (read momentum) to reach the vital organs.
You should also consider, when making your choice of calibre or load, that the higher the impact velocity, the greater the degree of resultant bruising (“blood-shot” meat that is unfit for human consumption). Likewise, the more fragile the bullet (the greater its potential for disintegration) the more bruising it causes. If you are strictly a trophy hunter, meat waste is not a consideration, but to biltong hunters it is anathema. By way of an (admittedly extreme) example, at a range of 50 metres, an impala shot through the shoulders with a .458 Win Mag (500gr bullet at 1900 fps) will suffer less meat bruising than if shot with a .270 Win using a 130gr bullet at 3000 fps. Neither choice is ideal, of course – I merely illustrate a principle.
It now comes down to choosing a calibre whose ballistics suitably match one or more of the six or seven different hunting categories we have in southern Africa. For reasons of brevity I will exclude the Big Five here, as well as hippo, and the so-called “tiny” antelope such as steenbuck, klipspringer, etc (only the most ardent trophy collectors take these little creatures seriously). I also exclude “varmint” hunting (small “pest animals” such as baboons, caracal, jackal, etc), likewise animals which fall into special categories, such as giraffe and crocodiles. Eland bulls also fall into in a category of their own – an eland bull is three times the weight of a kudu or gemsbuck bull (I consider the 9.3×62 and the .375H&H as ideal for eland bulls, regarding the .338 with 250gr bullets of very strong construction to be minimal).
This leaves us with four general categories of ungulates (hoofed animals) based on their live body weight in conjunction with their normal habitat. (1) Large ungulates (bulls weighing 250kg) in bushveld conditions (close to moderate range) e.g. kudu, blue wildebeest, zebra. (2) Large plains-dwelling ungulates (long range) such as gemsbuck, zebra and eland cows. (3) Small ungulates (rams weighing up to 70kg) in bushveld conditions, e.g impala, bushbuck. (4) Small plains-dwelling ungulates, e.g. springbuck, blesbuck. To split hairs, there is in fact a fifth category: medium weight ungulates (bulls averaging around 140kg) such as lechwe, hartebeest, nyala, but in terms of calibre choice, these can be lumped together with the large antelope. Likewise bushpigs and warthogs.
I cannot here expound fully on all the provisos that should attend this discussion, such as the advice to choose a calibre that you can shoot well with, rather than one whose recoil you cannot manage without flinching, etc, etc – all this is assumed. Likewise, we all know that “in the right hands” (etc, etc) a .30-06 or a .300 Win Mag can be successfully used for all four categories; that “real hunters” can stalk close enough to use a .303 on springbuck in open plains, while yet others just use a 7×57 for everything because they “only take head or neck shots”. I will approach this subject in terms of the “average” hunter looking for the “ideal” calibre/load for each category. Bear in mind that conditions are seldom perfect in the veld. You cannot count on animals to stand broadside – all too often they face you at an angle, and your bullet must smash through heavy shoulder bone, or they angle away from you, necessitating a raking shot through the abdomen, angled forward into the lungs. Such shots would require heavier, stronger bullets than would a broadside shot on the same animal. And always remember, the ethical hunter strives to avoid any possibility of wounding. He is not concerned with what a calibre/load can do, but with what it can be relied on to do.
Taking all the aforementioned into account, category (1) requires a minimum calibre of .308″ with a minimum bullet weight of 220gr if of ‘conventional’ (read ‘fragile’) design, or a minimum of 180gr if of ‘premium grade’ design (having special reinforcing features, e.g. Barnes-X, Swift A-frame, etc). If one of the .300 magnums is chosen for this category, only the strongest premium grade bullets should be used, irrespective of weight. In my opinion, a .338 bullet weighing 250gr would be more appropriate for this category (again, a premium grader if in a magnum version) while a 9.3×62 or a .375H&H would by no means be out of place, being considered by many to be ideal.
Category (2): the same bullet diameter and weight recommendations apply as for category 1, but due to the longer distances involved, faster calibres such as the .338 and .300 Win Mags make life easier (there is no need for the Weatherby or Ultra-Mag versions). The resulting lower impact velocities render ‘conventional’ bullets adequate enough, but I still prefer premium graders (you might just surprise a gemsbuck at moderate range). The .375H&H (with 270gr bullets) is also a fine choice in this category.
Category (3): The important factor here is moderate velocity (to avoid meat waste). Muzzle velocities between 2000 and 2300fps are ideal. Bullet diameter is not important – from 6mm (.243″) to .308″ is best. Bullet weight: anything from 100gr up. Ideal cartridges are the 6×45 with 100gr bullets (2300fps), the .30-30 Winchester with 170gr bullets, the .303 British with 215gr bullets. Conventional bullets are quite adequate. Again, be guided by velocity – if using a .30-06, rather use a 220gr bullet than a 150gr (to reduce meat bruising). If using a 7×57, choose 170gr bullets or heavier. Avoid the .243 Win, .270 Win, 7×64 or similarly fast calibres.
Category (4): Here the opposite applies – you need the higher velocities because at the longer distances involved, a springbuck’s vital area makes a very small target, so bullet drop is critical. The .243 Win is okay in windless conditions, but all told you are better off with a .270 Win with 150gr bullets, 7×64 or 7mm Rem Mag. Meat damage is always a problem in this category – the best way to avoid it is to take lung shots, aiming one inch behind the shoulder so as to avoid the muscle altogether (“rib-cage” shots). Conventional (rapidly expanding) bullets are best.
For a more comprehensive discussion on this and related subjects, refer to my book Rifles For Africa (available from Rowland Ward Publications, Johannesburg).