Compared: 7mm Rem. Mag. and .300 Win. Mag.
By Chuck Hawks
What rifle to buy, a 7mm Magnum or a .300 Magnum? (A better question might be, "do I need a magnum rifle at all?" but that has already been addressed in another article.) There are a number of 7mm and .300 Magnum cartridges, but the 7mm Remington Magnum and .300 Winchester Magnum are the best selling magnum cartridges in the world and the only magnum cartridges among the top 10 best selling rifle cartridges. They were not the first magnums introduced in either caliber, but they have become the standard of comparison.
The 7mm Rem. SAUM and 7mm WSM short action magnums were designed specifically to duplicate the ballistics of the 7mm Remington Magnum, which they do. The .300 WSM and .300 Rem. SAUM were designed to duplicate the ballistics of the .300 Winchester Magnum, and they do. Other standard length 7mm Magnums, such as the 7mm Weatherby Magnum, offer ballistics similar (if not identical) to the 7mm Rem. Mag. Other standard length .300 Magnums, such as the .308 Norma Magnum, perform much like the .300 Win. Mag.
So, for the purposes of this comparison, we are going to use the 7mm Rem. Mag. to represent all of the 7mm Magnums in its general performance class, and the .300 Win. Mag. to represent all .300 Magnums in its general performance class. The hope is that this article can help some Guns and Shooting Online readers answer the question at the top of this page for themselves.
The 7mm Remington Magnum
Remington introduced the most successful magnum cartridge of them all in 1962. It was 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, Mashburn, and 7x61 S&H 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 CXP2 and CXP3 game, particularly 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 Magnum also kicks about as hard as a .30-06, 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 both factory loaded ammunition and rifles to shoot it are available just about everywhere big game is legally hunted.
Remington factory loads for their 7mm Magnum include bullets of 140, 150, 160, and 175 grains. Bullets of around 150 grains seem to be about optimum for any 7mm Magnum rifle in terms of long range energy, 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 cartridges.
The .300 Winchester Magnum
For years wildcatters had been necking the .338 Winchester Magnum case down to accept .30 caliber bullets. Norma of Sweden commercialized such a cartridge as the .308 Norma Magnum in 1960. Winchester did not get around to introducing their .300 Magnum until 1963. But when they did, its sales left all other .300 Magnums in the dust.
The .300 Win. Mag. is not based on a necked-down .338 Mag. case. Instead, it is a different belted case based on a shortened .300 H&H with the usual .532" magnum rim diameter, but a longer 2.62" case length with minimum body taper and a very short neck to maximize powder capacity. (The .338 and 7mm Rem. Mag. cases measure 2.5" in length.) Since the .300 Win. Mag. must work in standard length actions, which requires a maximum cartridge overall length of no more than 3.34", its bullets are seated proportionately deeper in the case.
The .300 Winchester has proven itself a successful long range cartridge for CXP2 and CXP3 game, and it is used all over the world. Like all other .300 Magnum cartridges, it kicks too hard for most shooter's comfort. According to guides in both Alaska and Africa, accurate bullet placement is usually the biggest problem for their clients shooting a .300 Magnum rifle.
.300 Win. Mag. cartridges are loaded by all of the major ammunition companies. Most magnum rifles that are offered in 7mm Rem. Mag. are also offered in .300 Win. Mag., and both factory loaded ammunition and the rifles to shoot it are widely distributed.
All of the big .300s are probably at their best with 180 grain bullets, and that includes the .300 Win. Mag. That is the bullet weight that delivers the most energy downrange, and it is the bullet weight selected for this comparison. Remington offers a .300 Win. Mag. factory load that uses a 180 grain AccuTip boat-tail bullet that is similar in design and sectional density (SD) to their 7mm 150 grain AccuTip boat-tail bullet. That .300 Win. Mag. factory load has a MV of 2960 fps, and it is the specific load that we will use to represent the .300 Magnum cartridges.
The best way to compare cartridges that use bullets of different diameters is by choosing loads that use bullets that are similar in sectional density. In the case of a 7mm (.284") vs. .30 (.308") caliber comparison, the 150 grain 7mm and 180 grain .30 bullets are similar in SD. And those are the bullet weights that we are comparing.
We will compare our selected 7mm and .300 Magnum loads in bullet sectional density and ballistic coefficient (BC), bullet cross-sectional area, velocity, energy, trajectory, killing power, and recoil.
Both the 7mm Rem. Mag. and the .300 Win. Mag. are available in a wide range of factory loaded ammunition and rifles, so that is not a consideration with those two calibers. It likely would be a consideration with most of the other 7mm and .300 Magnum cartridges, none of which approach these two in popularity. The availability of factory loaded cartridges and production rifles is very important in the long run, so buyer beware if you are contemplating purchasing one of the lessor known magnums.
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 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 a minor advantage in SD. SD is not a direct factor in calculating BC, but when two bullets are of basically identical form, the bullet with the higher SD usually also has a superior BC.
Given bullets of identical construction, and other factors being equal, the 150 grain 7mm and 180 grain .300 bullets should offer similar penetration. In a practical sense this means that if a given 180 grain .300 bullet will shoot through both shoulders of an elk, so will a 150 grain 7mm bullet of the same design and construction.
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"; the bullet diameter of .300 Magnum bullets is .308". Following are the frontal areas of each in square inches.
As those numbers reveal, the .300 has a clear advantage over the 7mm in bullet frontal 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. And 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 .300 Win. Mag. loads, measured in 24" test barrels.
The 7mm Rem. Mag. bullet starts out 150 fps faster at the muzzle, and it is traveling 191 fps faster at 400 yards. Relatively speaking, it is pulling away from the .300 bullet throughout its flight. This will result in a flatter trajectory and less wind drift 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 very powerful. Any load that develops over 3000 ft. lbs. of muzzle energy has to be respected! The .300 Mag. starts out with a moderate 280 ft. lb. advantage, but this has decreased to only 33 ft. lbs. at 400 yards due to the superior BC of the 7mm bullet.
Trajectory is important to hunters because the flatter a bullet's trajectory, the easier it is to achieve accurate 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.
Remington ballistic tables show bullet drop based on a 200 yard zero. Here are the published trajectories for our loads (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 somewhat higher ballistic coefficient, it also shoots flatter. It is not shown by the figures above, but the maximum point blank range (+/- 3") of our .300 Win. Mag. load is 293 yards, compared to a maximum point blank range of 310 yards for our 7mm Rem. Mag. load. Remembering that it also carries almost an much energy out at 400 yards as the .300 Mag. bullet, 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 or .300 Magnums. 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 two of the relevant factors (impact velocity and bullet weight) 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 estimate the live animal weight at any specified 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 figures in pounds for our 7mm Rem. Mag. and .300 Win. Mag. loads from the muzzle to 400 yards. (For more on OGW, see the "Expanded Optimum Game Weight Table" on the Tables, Charts, and Lists Page.)
Because of its heavier bullet the .300 Mag. starts out with a 245 pound advantage in OGW at the muzzle (where both calibers are over 1000 pounds!) , and retains a 62 pound advantage at 400 yards. Both of these calibers are clearly capable of harvesting large animals, but it they are really big or potentially dangerous, like brown and polar bear, the .300 Win. Mag. has the advantage.
This is the category that magnum fans in general, and gun writers in particular, like 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 going off is a great wounder of game. Severe flinches result in those embarrassing "grounders" you sometimes see at the range. Anyone, no matter how big or strong or experienced, can shoot more accurately with a rifle that kicks less. That fact 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 .300 Win. Magnum loads (calculated using IMR 4831 powder) when 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 .300 Win. Mag. is substantially, and uncomfortably, over the limit. That, in a nutshell, is the problem with all of the .300 Magnum calibers and the biggest single advantage of the 7mm Rem. Mag. over the .300 Win. Magnum.
And, contrary to the advertising hype that you may have read, recoil is actually worse with the new short action Magnums because they are served-up in lighter weight rifles. Rifle weight is directly proportional to recoil. Reduce rifle weight from 8.5 to 7.5 pounds (about 12%) and recoil increases by about 12%. Simple physics. The bottom line is to avoid light weight rifles in any magnum caliber, and most certainly in a .300 Magnum.
Summary and Conclusion
The 180 grain .300 Winchester Magnum load is superior to the 150 grain 7mm Remington Magnum load in terms of bullet cross-sectional area, kinetic energy inside of 400 yards, and killing power. Only in cross-sectional area, however, is it actually dominant. The 7mm Magnum is superior to the .300 Magnum is sectional density, velocity, trajectory, and recoil. Only in (less) recoil is it markedly superior.
For the great majority of hunting conditions there is actually not a great deal of difference between these two big game cartridges. Nor is there much difference in the availability of rifles, ammunition, and reloading bullets. Both are popular calibers, among the top 10 in sales.
My analysis is that the .300 Magnum is generally superior at medium range and for use on very large, dangerous game (polar and Alaska brown bears). The 7mm Magnum is generally a better long range cartridge, and has the important advantage of lower recoil, which makes accurate bullet placement easier and more likely, especially at long range. Both calibers are good choices for hunting large, non-dangerous game (CXP3) such as North American elk.
Since very few modern hunters actually seek large, dangerous CXP3 class game, most are probably better off with a 7mm Magnum. It will do everything that they need to do, and they will likely shoot it more accurately than they could a .300 Magnum.
Copyright 2006, 2012 by Chuck Hawks. All rights reserved.