Compared: 7mm Magnum and .30-06 Springfield
By Chuck Hawks
What cartridge will best serve my needs, a 7mm Magnum or a .30-06? There are a number of 7mm Magnum cartridges, but the 7mm Remington Magnum is the best selling magnum cartridge in the world and the only one whose distribution and availability in a wide variety of rifles approaches that of the .30-06. Since the performance of most of the 7mm Magnums is similar, we will use the popular Remington version to compare to the .30-06 in this article. Keep in mind that the ballistics of the 7mm SAUM, 7mm WSM, 7mm S&H and 7mm Weatherby are similar. Hopefully, this comparison will help Guns and Shooting Online readers answer the question at the beginning of this paragraph for themselves.
The 7mm Remington Magnum
Remington introduced their 7mm Magnum cartridge in 1962, based on a necked-down .338 Win. Mag. case. This is, itself, a shortened (.30-06 length) and blown out version of the .300 H&H Belted Magnum case, with a standard .532" magnum rim diameter and a sharp 25 degree shoulder. Maximum cartridge overall length is specified as 3.29". Previous 7mm Magnums, among them the Weatherby and 7x61mm Sharpe & Hart versions, are similar in concept and performance, but it is the 7mm Rem. Mag. that caught the shooting public's fancy.
The 7mm Remington Magnum and all similar cartridges have proven excellent for use on Class 2 and Class 3 game, especially at long range. The popular saying that the 7mm Mags shoot as flat as a .270 and hit as hard as a .30-06 is not far off the mark. In rifles of typical magnum weight (about 8.5 pounds), the 7mm Rem. Magnum's recoil is within the 20 foot-pound limit, which means that it is within the reach of most experienced shooters. It is, however, not a cartridge for the inexperienced shooter.
All major ammunition companies load the 7mm Rem. Mag. cartridge. Most magnum rifle models are available in 7mm Rem. Mag. and factory loaded ammunition and the rifles to shoot it are available just about everywhere big game is legally hunted.
Remington currently offers 10 factory loads for their 7mm Magnum, loaded with bullets weighing 140, 150 and 160 grains. (Remington no longer loads a 175 grain bullet, but others do.) 150 grains seem to be about the optimum all-around bullet weight for any 7mm Magnum rifle, so that is the bullet weight that we will use for this comparison. Remington offers a 7mm Rem. Mag. load using their 150 grain AccuTip boat-tail bullet at a MV of 3110 fps and that is the specific load that we will use to represent the 7mm Magnum in this comparison.
The .30-06 Springfield
The .30-06 became the U.S. service cartridge in 1906. It was based on the previous .30-03 cartridge with a slightly shortened neck and loaded with a 150 grain spitzer bullet. The basic cartridge dimensions include a .473" rim diameter, .470" head diameter, .441" shoulder diameter, 17.5-degree shoulder angle, 2.494" case length and 3.340" maximum cartridge overall length.
The .30-06 is an exceptionally well balanced cartridge and it quickly became a favorite all-around hunting cartridge, widely used wherever big game in hunted. Almost every hunting rifle with a standard length action is offered in .30-06. The recoil in a typical eight pound hunting rifle remains below 20 foot-pounds with most loads, which means that the .30-06 can be controlled by most experienced shooters. However, it is not recommended for beginning hunters unless low recoil loads are used.
An exceptionally wide range of bullet weights are offered in .30-06 and virtually all ammunition manufacturers offer .30-06 factory loads. For example, Remington currently offers 20 different .30-06 loads using bullets weighing from 125-220 grains. Despite this embarrassment of riches, bullet weights of 150, 165 and 180 grains are by far the most popular. Many .30-06 fans consider the 165 grain bullet weight the best all-around choice and Remington offers an AccuTip boat-tail bullet at a MV of 2800 fps. This is the load we will use for this comparison.
We will compare our selected 7mm Magnum and .30-06 loads in bullet sectional density (SD) and ballistic coefficient (BC), cross-sectional area, velocity, energy, trajectory, killing power and recoil. Both the 7mm Rem. Mag. and the .30-06 are offered in an exceptionally wide variety of factory loaded ammunition and rifles, so availability is not an issue with these two calibers.
Sectional Density and Ballistic Coefficient
Sectional density is defined as a bullet's weight (in pounds) divided by the square of its diameter (in inches). Sectional density is important because the greater the SD, the longer a bullet is for its weight and, other factors being equal, a long skinny bullet of any given weight penetrates better than a short fat bullet of the same weight. Penetration is an important factor in the length of the wound channel, the amount of tissue disrupted and destroyed and thus killing power.
BC is a measurement of how well a bullet flies through the air. The higher the BC, the more aerodynamic the bullet and the lower its air drag. A higher BC helps a bullet retain more of its initial velocity and energy down range and results in a flatter trajectory. Here are the sectional densities and Remington's published ballistic coefficients for the bullets used in the loads compared in this article.
The 7mm/150 has the advantage in both SD and BC with these bullets of identical form. SD is not a direct factor in calculating BC, but when two bullets are basically similar, the bullet with the higher SD usually also has a superior BC. Given bullets of identical construction, other factors being equal, the 150 grain 7mm bullet should penetrate deeper than the 165 grain .30-06 bullet and also offer the advantages of a flatter trajectory.
Bullet weight has no bearing on frontal area, only caliber. 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. The actual bullet diameter of 7mm Magnum bullets is .284" and the bullet diameter of .30-06 bullets is .308". Following are the cross-sectional areas of each in square inches.
As those numbers reveal, the .30-06 has a clear advantage over the 7mm Magnum in cross-sectional area. This potential for a wider wound channel is probably the single most important reason for the perception that .30 caliber rifles kill better than 7mm rifles.
Higher velocity means flatter trajectory, given bullets of equal ballistic coefficient (BC). Velocity is also the most important component in the formula used to compute kinetic energy. Impact velocity may influence killing power, an assertion that is widely debated and not well understood, even by those who specialize in terminal ballistics. Here are the Remington velocity figures from the muzzle (MV) to 400 yards in feet-per-second for our selected 7mm Rem. Mag. and .30-06 loads, measured in 24" test barrels.
As expected, the 7mm Rem. Mag. has a decisive advantage in velocity at all ranges. The 7mm AccuTip bullet starts out 310 fps faster at the muzzle and it is traveling 376 fps faster at 400 yards. Relatively speaking, it is pulling away from the .30-06 bullet throughout its flight. This very substantial velocity advantage will give the 7mm Mag. a flatter trajectory and less wind drift, particularly at long range.
Kinetic energy is a measure of the ability to do work. The "work" in this case is penetrating deep into a game animal and powering bullet expansion. The key factors in computing kinetic energy are bullet mass and bullet velocity squared. Energy is an important factor in bullet performance and killing power. It is a good indicator of the power of similar rifle cartridges. Here are the Remington energy figures for our selected loads in foot-pounds from the muzzle (ME) to 400 yards.
These figures show that both calibers are quite capable for hunting Class 2 and Class 3 class game. However, the 7mm Rem. Mag. has a clear advantage over the .30-06 in kinetic energy at all ranges. The difference is 380 ft. lbs. at 100 yards and 420 ft. lbs. at 400 yards. You could summarize the situation by saying that the 7mm Mag. offers about 400 ft. lbs. more energy at most hunting ranges.
Trajectory is important to hunters, because the flatter a bullet's trajectory, the easier it is to achieve accurate bullet placement at unknown ranges and bullet placement is, by far, the most important factor in killing power. The primary factors influencing trajectory are velocity and ballistic coefficient.
Remington ballistic tables show bullet drop for our selected loads based on a 200 yard zero. Here are the published trajectories (in inches above or below the line of sight of a scope mounted 1.5" above the bore) out to 400 yards.
Not surprisingly, since the 7mm Mag. bullet has a higher muzzle velocity and a better ballistic coefficient, it shoots flatter. These figures also reveal that, out to 250 yards, the difference in trajectory is not very significant. However, remembering that the 7mm Magnum also carries more energy at all ranges, it would seem that, as a long range cartridge, the 7mm Mag. is the way to go.
Killing power is the most difficult factor to quantify. Bullet placement is the most important factor in a cartridge's effectiveness on game and that is largely a function of the shooter's skill and judgment. The construction and performance of a hunting bullet is also very important and practically every type of hunting bullet is available for either the 7mm Rem. Mag. or .30-06. Kinetic energy is one indication of potential killing power, as are bullet frontal area and sectional density, but none of these tells the entire story.
One attempt to include at least some of the relevant factors is the Optimum Game Weight (OGW) formula developed by Edward A. Matunas and published in the Lyman 47th Reloading Manual. To reduce the variables, Matunas started with the assumption that bullet design and placement are adequate for the task at hand. OGW is an attempt to quantify the live animal weight and maximum distance for which a hunting load is optimum. Thus, it compares the killing power of different cartridges and loads in a way that is relevant in the field.
Here are the OGW ranges from the "Expanded Optimum Game Weight Table" on the Tables, Charts, and Lists index page for the 150 grain 7mm Rem. Mag. and 165 grain .30-06 factory loads for 200 pound, 400 pound and 600 pound animals at any distance out to 400 yards. (Distances beyond 400 yards, which is well beyond the MPBR of either cartridge, are merely noted as "400+ yards.")
Both of these calibers are clearly capable of harvesting Class 2 and Class 3 animals at or beyond normal ranges, but our all-around 7mm Rem. Mag. load is superior for large animals, such as elk, as the range increases.
This is the category that magnum fans generally prefer to gloss over, but it is actually of crucial importance. Bullet placement is, by far, the most important factor in killing power and rifle recoil is the enemy of accurate bullet placement. A hunter who flinches in anticipation of the rifle firing will wound a lot of game. Severe flinches result in those embarrassing "grounders" you sometimes see at the range. Anyone, no matter how big, strong and experienced, can shoot more accurately with a rifle that kicks less. This has been demonstrated countless times. Here are some recoil energy (in foot pounds) and recoil velocity (in feet-per-second) figures for our 7mm Rem. and .30-06 loads fired in 8.5 pound rifles.
If you accept the common generalization that the average shooter cannot long tolerate recoil above about 20 ft. lbs. without developing a flinch, and I do, then the 7mm Rem. Mag. squeezes under the permissible recoil limit and the .30-06 gives the shooter a little more breathing room. The difference is noticeable and favors the .30-06.
Rifle weight is directly proportional to recoil. Reduce the weight of a .30-06 rifle from 8.5 to 8.0 pounds (a fairly typical weight for a .30-06 sporter) and the recoil increases to about 18.7 ft. lbs. and 12.3 fps. The lesson here is that a 7mm Mag. rifle needs to weigh about ½ pound more than a .30-06 rifle to keep the recoil at similar levels.
Summary and Conclusion
The 7mm Magnum and .30-06 are outstanding all-around hunting rifle cartridges. The 150 grain 7mm Remington Magnum load is superior to the 165 grain .30-06 load in terms of bullet SD and BC, velocity, energy, trajectory and OGW killing power. The .30-06 wins in the areas of bullet cross-sectional area and lower recoil. .30-06 factory loaded ammunition is usually a bit less expensive than 7mm Remington Magnum ammunition.
For most hunting conditions at medium range there is actually not a lot of practical difference in capability between these two fine big game cartridges. Nor is there a definitive difference in the availability of rifles, ammunition and bullets for reloading. Both are popular calibers, among the top 10 in sales, and well proven on all sorts of big game around the world. Most hunters will be well served by either.
My opinion is the .30-06 is probably superior at moderate range for use on very large game, such as Alaskan moose and the great bears, due to the availability of heavy 180-220 grain bullets in the caliber and its greater cross-sectional area. The 7mm Remington Magnum is a better long range cartridge for shooting Class 2 or Class 3 game.
Both calibers are a good choice for mixed bag hunts, such as mule deer and elk in North America. They are an equally good choice for African plains game hunts. These cartridges are unnecessarily powerful and consequently kick harder than necessary for hunting the smaller species of Class 2 game, such as pronghorn antelope and small to average size North American deer. The 7mm Remington Magnum and .30-06 Springfield both made the short list of four top all-around calibers, along with the .270 Winchester and .308 Winchester. (See "All Around Rifle Cartridges" on the Rifle Information page for details.)
Copyright 2013 by Chuck Hawks. All rights reserved.