The Great All-Around Rifle Cartridge Comparison:
By Chuck Hawks
Readers of my article "The All-Around Rifle Cartridges" will recognize the four cartridges in the title of this article as constituting the final short list of all-around rifle cartridges.
The definition of an all-around hunting cartridge is one that can reasonably be used in a single rifle, with appropriate loads, for a wide variety of game. Game from the size of a small animal like a coyote, chamois, or javelina up to large (at least 500 pound average live weight) thin-skinned game like elk, alg or kudu.
Further, the all-around cartridge should have a flat enough trajectory to allow hunting in a variety of conditions, from deep woods to open plains or high mountains. This means it has to have a maximum point blank range (MPBR) +/- 3" of at least a 250 yards. In general terms, it should be able to drive a spitzer bullet with a sectional density of at least .220 to a muzzle velocity of at least 2,700 fps.
Once a master list of cartridges that fufilled that basic definition was compiled they were judged against a number of criteria. These criteria included recoil (which must be manageable), bullet selection (in factory loads and available to reloaders), the availability of rifles, and the availability of ammunition (both in North America and world-wide). The four cartridges that made the list in every category are the four that are the subject of this comparison.
Clearly, all four are fine all-around cartridges with a great deal of overlap in their strengths and capabilities. These are, on balance, the best such cartridges in the world. No one seeking an all-around hunting cartridge can go seriously wrong with any of them. Yet, they are not identical. So it is perhaps reasonable to compare the four against each other. That is the rationale for this article.
I have written fairly extensive articles about all four of these cartridges. To save space in this article I am going to write only a very brief introduction to each, and refer those who are interested in reading more about the .270 Winchester, 7mm Remington Magnum, .308 Winchester, and .30-06 Springfield to those individual articles, which can be found on the Rifle Cartridge Page.
The famous .270 was introduced in 1925 to an indifferent shooting world that took little notice of the new cartridge. For many years after its introduction it was the highest velocity, flattest shooting big game cartridge available from a major manufacturer. A number of gun writers, including Jack O'Connor "the Dean of American Gun Writers," tried the cartridge, liked it, and began to sing its praises.
As the years went by .270 rifle and ammunition sales gradually increased until, ultimately, it became the second most popular big game cartridge in North America and was distributed and used world-wide. It is the only cartridge to seriously challenge the popularity of the .30-06 and is now available in practically every hunting rifle with an action long enough to accept it.
Unlike the .270, the 7mm Remington Magnum was an overnight success. Immediately following its introduction in 1962 buyers were clamoring for rifles in the new caliber, and for a long time Remington was unable to keep up with the demand.
Remington's Big 7 has never looked back. Today it is the best selling magnum cartridge in the world and, according to most lists, the 6th best seller amongst all big game cartridges.
The .308 was developed as the T65 experimental cartridge by Winchester and the U.S. Army in the early 1950's as the military replacement for the venerable .30-06. Winchester introduced the short action .308 as a civilian cartridge in 1952; in 1954 it was adopted by the U.S. military as the 7.62 NATO.
Like almost all successful military cartridges, the .308 also became a popular hunting cartridge. Because it is adaptable to today's popular short action rifles, the .308 is probably available in more different rifle models than any other all-around cartridge. It is the 4th best selling big game cartridge on most lists, behind only the .30-06, .270, and .30-30.
The .30-06 is the best known and best selling big game rifle cartridge in the world. It has been used successfully on every species of North American big game and has probably killed more CXP2 and CXP3 class game than any other cartridge except for the .30-30.
The .30-06 was developed from the earlier and very similar .30-03 by the U.S. military in 1906, and served very successfully through two World Wars and the Korean War. It requires a long action rifle, which was why it was finally replaced in military service by the .308 Winchester in 1954. But in the game fields of the world it has yet to be replaced, or even equaled, by any other cartridge.
In the course of this article we will compare the velocity, energy, trajectory, bullet frontal area, sectional density, killing power, and recoil of representative factory loads for each caliber. We will end with a look at some additional factors not related to ballistics.
There are a plethora of loads and bullet weights for all three cartridges, so to keep this project maneagable we are going to use the two most popular (and roughly comparable) bullet weights in each caliber. The lighter bullet is generally preferred for CXP2 class game (deer, goats, antelope, sheep) and shoots flatter. The heavier bullet is generally preferred for heavier CXP3 class game (elk, alg, kudu) and features increased sectional density for deeper penetration. The following factory load ballistics were all taken from the Winchester Ammunition 2004 Product Guide and use bullets of similar design in an attempt to make the comparison as fair as possible. All ballistics were developed in 24" barrels. (Caliber - bullet, MV, ME):
This list gives the muzzle velocity (MV) and muzzle energy (ME) for each load, so they are easy to compare.
Higher velocity means flatter trajectory, given bullets of equal ballistic coefficient (BC). Velocity is also an important component in the formula used to compute kinetic energy.
The lighter bullet in each caliber (.270/130, 7mm/140, .308/150, and .30-06/150) achieves the highest velocity. As one might expect, the .270 and 7mm Mag. have the advantage here, with the 150 grain .30-06 and .308 bullets lagging by about 200-290 fps.
The .270 and 7mm Mag. retain their velocity advantage when the heavier bullets in each caliber are compared (.270/150, 7mm/160, .308/180, and .30-06/180). The .270 and 7mm Mag. are within 20 fps of each other, but the .30-06 trails by about 200 fps and the .308 by more than 300 fps.
Clearly, the .270 and 7mm Mag. win the velocity comparison, with the 7mm Rem. Mag. shading the .270 Win. by a very small margin.
Bullet energy is easy to compute and widely compared. Kinetic energy, measured in "foot pounds" (ft. lbs.) is an important factor in, but not the whole story of, a cartridge's potential killing power. Energy is a way to measure the ability to do "work," which in this case means power the bullet expansion and penetration necessary to humanely kill game.
A quick perusal of our list of factory loads (above) reveals that the lighter bullets in each caliber carry about 100-200 ft. lbs. less energy at the muzzle than the heavier bullets. Yet the lighter bullets in each caliber generate from 2629 ft. lbs. (.308 Win.) to 2988 ft. lbs. (7mm Mag.) of muzzle energy.
It is estimated that, given proper bullet placement, about 800 ft. lbs. of remaining energy are required for reliable and humane kills of CXP2 class game. At 500 yards, far beyond the maximum point blank range of all of these cartridges, the 150 grain .308 bullet is still carrying 1147 ft. lbs. of kinetic energy.
The 7mm Magnum wins the energy comparison with either bullet weight, but not by a great margin. Energy is not the critical factor in killing power for any of these loads. All are more than sufficient for their intended purpose at any reasonable range.
Trajectory is important to hunters because the flatter the bullets trajectory the easier it is to achieve precise bullet placement at long and unknown ranges. And bullet placement is, by far, the most important factor in killing power. The primary factors influencing trajectory are bullet velocity and ballistic coefficient. I intentionally chose factory loads with similar bullets for this comparison to minimize the effect different style bullets has on BC. Bullets with greater SD naturally tend to have a higher BC.
Ammunition catalogs usually show bullet drop at 100 to 500 yards with a 200 yard zero. But a better way to compare trajectory is by maximum point blank range. The MPBR, for our purposes, is the distance over which the bullet neither rises nor falls more than 3" from the line of sight. This allows the hunter to use a center hold on even small big game animals (like pronghorn antelope) without having to worry about "holding over" unless the MPBR is exceeded. Here is the MPBR for our selected loads, courtesy of the ballistics calcualtor at BigGameInfo:
(* Partition Gold bullet [BC .474] substituted for Silvertip bullet for uniformity)
The flat shooting 140 grain 7mm Remington Magnum bullet has only a 9 yard advantage in MPBR over the standard .270 Winchester, and the .270 has a 13 yard advantage over the .30-06 and a 21 yard advantage over the .308 Winchester when the trajectories of the lighter bullets in each caliber are compared. With the heavy bullets the .270 and 7mm Mag. are virtually tied, and they hold a modest advantage over the .30 caliber contenders
Bear in mind that most big game animals are killed within 100 yards, and very few beyond 250 yards (despite what you read in the popular sporting press), and it becomes clear that all four calibers, with all loads, have a satisfactory MPBR for the great majority of hunting situations.
The biggest cases and the lightest bullets are always going to win this kind of comparison. Accordingly, the 7mm Mag. and .270 Win. are the flattest shooting of our four all-around calibers, and probably the best choices for the hunter that does a lot of long range shooting (something that should be avoided whenever possible).
Bullet Frontal Area
The cross-sectional area of a hunting bullet is important because, other factors being equal, the fatter bullet makes a wider wound channel and damages more tissue. This translates to quicker and more humane kills. Bullet weight has no bearing on frontal area, only caliber. The actual bullet diameter of .270 Winchester bullets is .277"; the diameter of 7mm bullets is .284"; the diameter of both .308 Win. and .30-06 bullets is .308". Here are the frontal areas of each:
As those numbers reveal, there is really not much difference between the .270 and 7mm in cross sectional area. On the other hand, the .30 calibers have a clear advantage over both. This potential for a wider wound channel is probably the single most important reason for the perception that .30 caliber rifles kill better than the smaller calibers, and it constitutes a real advantage for the .308 and .30-06.
Wound channels have depth (length) as well as diameter. And the sectional density of the bullet, other factors being equal, greatly influences the depth of penetration. The higher the SD the greater the potential for penetration.
It is a combination of wound channel diameter and length that determine the total amount of tissue damaged by a bullet, and consequently how well it kills. Obviously, a bullet must penetrate into an animal's vitals to insure a quick and humane kill. This is why calibers that fire bullets of high SD, such as the 6.5x55 and .338 Magnum, have such excellent reputations as killers of tough big game. Here are the SD numbers for the calibers and bullets we are comparing:
In terms of SD, and potential penetration, the smaller calibers in our comparison have the advantage. This is important, but widely misunderstood, as many shooters incorrectly equate penetration with bullet weight. Bullet weight per se is not a factor in penetration. For more on the subject of sectional density, see my article "The Sectional Density of Rifle Bullets" on the Rifle Information Page.
The .270/130 and 7mm/140 grain bullets are clearly superior in SD to the 150 grain .30 caliber bullet. The heavy .270/150 and 7mm/160 grain bullets are somewhat superior to the 180 grain .30 caliber bullet. This advantage in penetration tends to balance the .30 calibers advantage in wound channel diameter.
Which brings us to the most controversial subject we must consider, killing power. There are lots of formulas and methods for estimating killing power (momentum, pounds-feet, various knock-out and stopping power values, etc.). Most were created by individuals with a bias against kinetic energy as an indication of killing power, and a bias in favor of some other factor, such as big diameter bullets, extreme velocity, bullet weight, etc. None of these theories have a particularly high correlation with reality. In fact, simple kinetic energy, which can be found in any ammuntion catalog, is probably a better indication of the killing power of big game rifle cartridges than any of them.
The best system that I have encountered for estimating the killing power of specific big game hunting rifle loads, and the only one I know of that attempts to account for all of the factors we have compared above, was developed by Edward A. Matunas and published in the Lyman 47th Reloading Handbook. It is not perfect, but it gets you in the ballpark and correlates well with reality. He calls it the "Optimum Game Weight Formula," and I thought enough of it to apply it to a great number of cartridges and loads, which you can see in my "Optimal Game Weight Table" on the Tables, Charts and Lists Page.
Here are the maximum optimal game weights (the live animal weight) for our eight loads at 250 yards:
Judging by these numbers, the 7mm Rem. Mag. has the advantage with light bullets, and the 7mm Mag. and .30-06 share the advantage with heavy bullets. The other calibers and loads are distributed between these benchmarks. There is very little difference, for example, between the .270 and .308 with either load.
The recoil or "kick" developed by any rifle/cartridge combination is very important regardless of the courage, size or strength of the shooter. Virtually everyone can shoot more accurately with a rifle that kicks less. This is true of even the dyed in the wool big bore shooter who distains any rifle with a bore measuring less than .40 caliber. The best shooting is done with the rifles that kick the least; just look at the results from practically any of the target shooting games for confirmation. Remember that bullet placement is, by far, the most important ingredient in killing power. And no one can consistently put a bullet into the vitals of a game animal with a rifle that causes them to flinch. Here are recoil numbers for our various loads, calculated for rifles weighing a uniform 8 pounds by the recoil calculator at Handloads.Com:
These numbers demonstrate than none of these cartridges are light kickers in standard weight rifles. All loads except the .270/130 and .308/150 are above the 15 ft. lbs. recommended for consistant accuracy, and two (the 7mm Mag./160 and .30-06/180) are slightly above the 20 ft. lb. "do not exceed" limit.
In terms of recoil energy, the .270 and .308 with their lighter bullets are the winners, and the 7mm Rem. Mag. and .30-06 with heavy bullets are the losers. The other loads are marginal, over 15 ft. lbs. but under 20 ft. lbs. of recoil energy. All of these cartridges kick too hard for use in light weight or mountain rifles; that is what the .243/6mm, .257, and .264/6.5mm caliber cartridges are for.
In particular, light weight rifles in .30-06 and 7mm Magnum should be avoided. In fact, even standard weight (8 pound) rifles in 7mm Magnum should be avoided. 7mm Magnum rifles should weigh at least 1/2 pound more than rifles chambered for standard cartridges. Fortunately, most 7mm Rem. Mag. rifles do weigh around 8.5 pounds (including scope and mounts). Here are recoil figures for our two magnum loads fired in 8.5 pound rifles:
The extra weight brings Remington's Big 7 back into the marginal class. That is basically the trade off required by the 7mm Rem. Mag., carry a half pound heavier rifle and reap the reward of superior ballistics. Or, seen from a different perspective, the rewards are not that much greater, but the rifle is not that much heavier, either.
All four of these cartridges are among the 10 best selling centerfire rifle cartridges. Ammunition for all four is distributed world-wide and is generally easy to obtain. Bullets and reloading components are legion. However, it is a fact of marketing that magnum ammunition generally costs more than standard calibers, even on sale. This means that it generally costs more to feed a 7mm Rem. Mag. rifle than any of the other calibers.
The .308 Winchester has one big advantage over all of the other cartridges: it was designed for use in short action rifles. The others all require a standard length action. This means that there are simply more makes and models of rifles available in .308 than in the other calibers. This is not usually much of a problem, as the other cartridges are available in a wide selection of action types, brands and models, but it remains a fact. The shooter who falls in love with, say, a Kimber Model 84M Classic rifle will find that it is available only in short action calibers, including the .308 Winchester.
Its design also makes the .308 inherently more reliable in autoloading rifles, for which it was originally designed. If your idea of an ideal all-around rifle is an autoloader, the .308 is the sensible choice.
The 7mm Rem. Mag., on the other hand, requires not only a standard length action, but a magnum action. These are common, and Remington's Big 7 is the best selling of all magnum rifles and cartridges, but it is another limiting factor. Some rifles that are available in .270 or .30-06 are not available in 7mm Rem. Mag., although most are.
Purely in terms of ballistics, the 7mm Rem. Mag. lives up to its reputation for shooting as flat as a .270 and hitting as hard as a .30-06. It does not have a lot of superiority over the other cartridges, but in most areas it has some. Objectively, it is the winner of this comparison as long as the hunter does not mind the extra rifle weight. The hunter who wants a flat shooting, standard weight rifle would do well to stick with the .270 Winchester.
BUT, and these are important qualifications, the 7mm Magnum also kicks the hardest in rifles of equal weight and requires a rifle with a standard length magnum action. Most 7mm Rem. Mag. rifles are indeed shipped with 24" barrels, but most .270, .308, and .30-06 rifles are shipped with 22" barrels. This detracts somewhat from their ballistics, but makes them handier in close quarters.
Chopping the barrel of a 7mm Magnum down to 22" is simply not a viable option. The result is a blowtorch with terrific muzzle blast and ballistics no better than a .270 Winchester. As the longer and heavier rifle, a 7mm Magnum is generally not the best choice where compactness and portability are important factors.
If real compactness and portability are desired in a standard weight rifle, the .308 Winchester is the stand out cartridge in the group. It is the only cartridge designed for use in short action rifles, which automatically saves about 1/2" in overall length and a few ounces in weight. And, because its shorter case holds somewhat less powder than the others, a 22" barrel detracts less from its ballistics.
So while the 7mm Remington Magnum probably produces the best ballistics, it may or may not be the best choice for an all-around rifle cartridge. That depends on the shooter and the specific applications for which the rifle is purchased. Choose wisely.
Copyright 2004, 2012 by Chuck Hawks. All rights reserved.