Compared: The 7mm Remington Magnum and .338 Federal
By Chuck Hawks
This is, on the face of it, a rather pointless comparison. It is an "apples to oranges" situation, since the 7mm Remington Magnum and .338 Federal are different types of rifle cartridges. I wouldn't be writing this article if Federal Cartridge had not made the comparison inevitable by using it in the advertising for their new .338 cartridge.
Why they didn't choose to compare the .338 Federal to the .358 Winchester, its natural rival, I can only speculate--but will not. We at Guns and Shooting Online have compared the .338 Federal to the .358 Winchester, and you can find that article on the Rifle Cartridge Page. Both cartridges are also included in the article, "The Great North American Medium Bore Rifle Cartridge Comparison," also on the Rifle Cartridge Page.
But, since Federal did choose to compare their short action .338 to the 7mm Rem. Magnum, this article is the result. Be advised that I personally like and use both cartridges for their intended purposes, so I own both dogs in this fight! Okay, here we go . . ..
The 7mm Remington Magnum
Remington's Big 7 was introduced in 1962 and has gone on to become the most popular magnum big game cartridge in the world. It is based on a necked-down .338 Win. Mag. case.
The popular way to summarize the performance of the 7mm Remington Magnum is that it shoots as flat as a .270 and hits as hard as a .30-06. Actually, it hits harder than a .30-06, but still, that is not a bad description. It is an outstanding all-around (CXP2 and CXP3) big game cartridge, and one of only four cartridges to make our "short list" of such cartridges.
Because it is so popular there are a plentitude of factory loads offered for the 7mm Rem. Mag. Practically everyone who loads center fire ammunition offers cartridges in 7mm Remington. Federal Cartridge alone offers 13 loads under the Federal brand and 2 more under the Fusion brand. For big game hunting the most popular bullet weights are 139-145 grains, 150-154 grains, 160-162 grains, and 175 grains.
To eliminate as many variables as possible, we will use two Federal Vital-Shok factory loads to represent the 7mm Rem. Mag. Our long range load will use the 150 grain Nosler Ballistic Tip (BT) bullet at a muzzle velocity (MV) of 3110 fps. To represent a heavy bullet load we will use the 160 grain Nosler Partition (NP) at a MV of 2950 fps.
The .338 Federal
Introduced for 2006, the .338 Federal is perhaps the most sensible medium bore rifle cartridge to come down the pike in quite a while. It is a short action cartridge based on a necked-up .308 Winchester case and its ballistics are close to those of the standard length .338-06 A-Square, just as the ballistics of the two parent cartridges are similar. Like the .308, the .338 Federal is loaded to maximum pressure in order to achieve its published ballistics in a 24" barrel.
Federal offers four loads for the .338, three in their premium Vital-Shok line and one in the Fusion line. These include a 180 grain Nosler AccuBond bullet at a MV of 2830 fps, a 185 grain Barnes Triple-Shock bullet at a MV of 2750 fps, a 210 grain Nosler Partition bullet at a MV of 2630 fps, and a 200 grain Fusion bullet at a MV of 2725 fps. Of these, the 180 grain Nosler AccuBond (AB), which has the same basic form as the Nosler Balllistic Tip, is the flattest shooting and the 210 grain Nosler Partition (NP) is the best choice for large game, so those are loads that we will use in this comparison.
We will compare our selected 7mm and .338 loads in bullet sectional density (SD) and ballistic coefficient (BC), bullet cross-sectional area, velocity, energy, trajectory, killing power, and recoil. And summarize at the end with a few concluding paragraphs.
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 penetrates better than a short fat bullet. Penetration is an important factor in the length of the wound channel, the amount of tissue disrupted and destroyed, and thus killing power.
Ballistic coefficient 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 published ballistic coefficients for the bullets used in the loads compared in this article.
It is obvious when comparing the lighter bullet in each caliber that the 7mm Mag. is superior in both SD and BC. Ditto when comparing the heavier pair of bullets. As 7mm is the smaller caliber, this is somewhat expected. What is noteworthy is that the 150 grain 7mm bullet is similar to the 210 grain .338 bullet in SD. We will see how this affects the results as we move along in our comparison.
Bullet weight has no bearing on cross-sectional (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 Remington Magnum bullets is .284". The bullet diameter of .338 Federal bullets is .338". Following are the frontal areas of each in square inches.
Obviously, if expansion percentage is identical, a .338 bullet will always punch a larger diameter hole than a 7mm bullet. This is the main reason for the existence of the medium bore calibers.
Higher velocity means flatter trajectory, given bullets of equal ballistic coefficient. Velocity is also the most important component in the formula used to compute kinetic energy. And impact velocity may directly influence killing power by means of "shock," an assertion that is widely debated even by those who specialize in terminal ballistics. Here are the Federal velocity figures from the muzzle to 400 yards in feet-per-second for our selected 7mm Rem. Mag. and .338 Federal loads, measured in 24" test barrels.
The 7mm Rem. Mag. dominates the velocity comparison with both bullet weights and at all ranges. Considering its lighter bullets and much bigger case, this is not surprising.
Kinetic energy is a measure of the ability to do work, and it is widely used to compare the power of rifle cartridges. Energy powers bullet penetration and expansion, very important elements in killing power. The key factors in computing kinetic energy are bullet mass and bullet velocity squared. Here are the Federal 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 is right up there! And the .338 Federal is competitive with the 7mm Mag., at least within 100 yards.
The 180 grain .338 bullet starts out with impressive ME, but sheds its energy relatively quickly due to the inferior BC of its bullet. The 7mm Rem. Magnum's 150 grain bullet rapidly pulls away from the .338 Federal's 180 grain bullet and carries the most energy of all our loads beyond 100 yards. The 210 grain .338 bullet has the most energy of all loads at the muzzle (albeit only by 5 ft. lbs. over the 7mm/150), and stays competitive with the 7mm/160 load out to 200 yards. This is due to the extra weight of the .338 bullet, and it is quite a tribute to the performance of the .338 Federal considering the discrepancy in the size and powder capacity of the two cases.
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, need I mention, bullet placement is the most important factor in killing power. The primary factors influencing trajectory are bullet velocity and ballistic coefficient.
Federal 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) from 100 to 400 yards.
Another way to compare the trajectory of hunting loads is by their maximum point blank range (MPBR). Here is the MPBR (+/- 3") for all of our loads. MPBR is the distance at which the bullet drops 3" below the line of sight and represents the longest range at which shots at big game animals should be taken.
There can be no doubt that the 7mm Rem. Mag. shoots appreciably flatter than the .338 Federal any way that you choose to compare the two cartridges. This is because of the 7mm Mag's higher velocity and superior BC. For long range shooting the 7mm Magnum is a far better choice. However, keep in mind that the .338 Federal was not intended to be a long range cartridge in the first place. It was designed to put the crunch on large animals without the excessive recoil of a medium bore magnum cartridge.
Killing power is the most difficult factor to quantify. Optimum Game Weight (OGW) is a system devised by Edward A. Matunas to express the killing power of rifle cartridges in terms of an animal's live weight and the optimum distance at which it can be taken with a given cartridge and load. Thus it compares the killing power of different cartridges and loads in a way that is relevant in the field.
To reduce the variables, Matunas started with the assumption that bullet design and placement are adequate for the task at hand. We needn't go into the formula itself here, suffice to say that while not perfect, the OGW system does seem to have a higher correlation with reality than most other systems for estimating the killing power of big game rifle cartridges. (For more on OGW, see the "Expanded Optimum Game Weight Table" on the Tables, Charts, and Lists Page.) The figures below represent optimum game weight in pounds and distance in yards from the muzzle to 400 yards.
Did I mention earlier that the whole point of the .338 Federal was to put down large animals without magnum recoil? It is killing power that validates that approach, and here the .338 Federal is competitive with the much larger cased 7mm Rem. Mag.
This is particularly true if you ignore the numbers beyond 300 yards, which is about the MPBR of the 7mm Mag. and well beyond the MPBR of the .338 Federal. The 180 grain .338 load is superior in OGW to the best 7mm Mag. load within 100 yards, where most big game is actually shot. And the 210 grain .338 load is superior in OGW to the best 7mm Mag. load to beyond 200 yards. Judging by these OGW figures, both 7mm Mag. loads and the .338/210 load are 300 yard elk cartridges. Remember, though, that the MPBR of the latter is 258 yards.
There are a couple of other interesting points about this OGW comparison. First, the 150 grain 7mm Mag. load is superior to the heavier 160 grain bullet at all ranges. This shows that the 7mm Rem. Mag. reaches its optimum performance with bullets weighing around 150 grains, and its performance actually decreases with heavier bullets. I have always found it hard to understand the popularity of the 160 grain bullet in this caliber.
Second, since the .338 Federal is not a long range cartridge in the first place, the relatively heavy 210 grain Nosler Partition bullet is the optimum choice among the factory loads for the caliber. It is superior in energy and OGW, as well as having achieved an outstanding record of performance on large game animals.
Free recoil energy
This is the category that fans of magnum cartridges and heavy bullets 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 #1 enemy of accurate bullet placement. A hunter who flinches in anticipation of the rifle firing is a great wounder of game. Here are some approximate recoil energy (in foot pounds) figures for our 7mm Rem. Mag. and .338 Federal loads when fired in 8 pound rifles. I've also included the .338 Win. Mag. (as loaded by Federal) for comparison. The free recoil energy figures below were calculated by the Remington Shoot ballistic program.
These numbers show that the .338 Federal kicks noticeably harder than the small bore 7mm Remington Magnum when shooting the 210 grain bullet (heavier bullets usually mean heavier recoil), and about the same when shooting the 180 grain bullet. However, it kicks a lot less than the .338 Win. Magnum (and most other medium bore cartridges), which in my opinion is the real justification for the .338 Federal's existence.
Actually, I like to handload a 200-210 grain bullet at a MV of 2400 fps to reduce the .338 Federal's free recoil energy in an 8 pound rifle to between 17 and 18 ft. lbs. This brings it below the 20 ft. lb. maximum generally recommended for experienced shooters. Such a load duplicates the performance of the .338x57 O'Connor and .338 Marlin Express wildcat cartridges and makes for a relatively pleasant shooting--yet still deadly--medium bore cartridge.
Summary and conclusion
The 7mm Remington Magnum is one of the most successful cartridges, and the most successful magnum, ever designed. It offers a fine balance of flat trajectory, killing power and controllable recoil, and it is one of the best long range and all-around big game cartridges in the world.
The .338 Federal is close to ideal for the woodsman hunting deer, black bear, and elk. It lacks the long range punch of a magnum, but the fact is that most big game animals are killed at less than 100 yards, and very few are actually killed beyond the MPBR of the .338 Federal. Instead of long range capability that will hardly ever be needed, it offers bullets of substantial diameter and weight that tend to get through brush better than smaller, lighter bullets. And it kicks much less than the medium bore magnums. It does, however, kick as much or more than the .30-06 and 7mm Remington Magnum.
In this comparison the 7mm Remington Magnum proved superior to the .338 Federal in most categories. Those strengths are what make it such a great all-around cartridge. On the other hand, the .338 Federal proved to be very good in its intended role, which is killing big animals at medium range, especially with the 210 grain bullet.
As I wrote at the beginning of this article, this is sort of an "apples to oranges" comparison that really sprang from the creative mind of Federal's resident advertising genius. I like both cartridges. Sure, there is some overlap, but they excel in different roles. I like the 7mm Rem. Mag. as an all-around, 300 yard CXP2 and CXP3 game cartridge. And I like the .338 Federal as a CXP3 game cartridge within 250 yards. I'd choose the 7mm Rem. Mag. for a combination mule deer and Rocky Mountain elk hunt. And I'd choose the .338 Federal for a combination black bear and Roosevelt elk hunt in the Pacific Northwest.
Copyright 2006, 2012 by Chuck Hawks. All rights reserved.