Compared: The Standard .338 Calibers
(.338 Federal, .338 Marlin Express,
.338x57 O'Connor, .338-06 A-Square)

By Chuck Hawks

Like the article "Compared: the .35 Calibers" (see the Rifle Cartridge Page), but unlike most other Guns and Shooting Online cartridge comparison articles, the intent here is to compare these cartridges in terms of their purpose and application as hunting cartridges, rather than to concentrate on their comparative performance per-se.

The field of reasonably well known, standard (non-magnum) .338 caliber cartridges has grown to four. All were formerly wildcats, but three are now factory loaded. So, let's take a look at our .338 caliber cartridges.

.338x57 O'Connor wildcat

The .338x57 wildcat cartridge was proposed by the Dean of American Gun Writers, Jack O'Connor, before the start of the Second World War. His suggestion was that a 7x57 Mauser case necked-up to accept .33 caliber bullets weighing about 200 grains at around 2400-2450 fps would make a nifty woods cartridge for deer, black bear, and even elk size game. He felt that the .35 Remington could use more punch and that the .348 Winchester kicked too hard for the average shooter. (Those were the two most popular American medium bores of that time, and he was right on both counts.)

The .338x57 was intended to keep recoil below 20 ft. lbs. (the nominal limit for the average shooter) and deliver more power than the .35 Remington. The 7x57 case has a long neck suitable for .338" bullets and enough cartridge overall length (COL) to avoid seating bullets too deeply into the case.

All of this made perfect sense to those of us at Guns and Shooting Online, so in 2004 I got in touch with Bradford O'Connor (Jack's son), and then wrote a series of articles about the .338x57. I called it the ".338x57 O'Connor" in Jack's honor, and my intent was to acquaint shooters with Jack's idea and promote the concept of a medium power, controlled recoil, medium bore cartridge to the rifle and ammunition manufacturers. (See the Wildcat Cartridge and Rifle Information pages for more information about the .338x57 O'Connor.) The idea apparently hit a responsive chord, as we got a lot of positive feedback from Guns and Shooting Online readers from those articles. Unfortunately, none of the rifle or ammunition manufacturers that we queried seemed interested in the idea.

Loaded to similar pressure, the .338x57 would outperform the .338 Federal due to its slightly larger case, longer neck, and more generous cartridge overall length. However, maximum performance was not the motivation behind the .338x57. Typical loads for the .338x57 would include a 200 grain flat point bullet at a moderate muzzle velocity (MV) of 2400 fps and a 225 grain spitzer bullet at a MV of 2300 fps. There are a plethora of .338" bullets between 180 and 225 grains from which to choose, and plenty of suitable powders for such a cartridge, so working up loads should not be a problem.

.338 Marlin Express

Toward the end of 2008, Hornady and Marlin formally introduced a new rimmed cartridge for the Model 336XLR lever action rifle named the .338 Marlin Express. This cartridge uses a new 200 grain Hornady Flex-Tip spitzer bullet and the latest non-canister powders to achieve a MV of 2565 fps. The .338 Marlin is big news for traditional lever action rifle fans.

The .338 and .308 Marlin Express cartridges have convincingly demonstrated what can be accomplished by using the latest propellants in relatively small cases. The .338 Marlin case has a little less powder capacity than the .338 Federal case, but that is not a problem, as its performance on large game is excellent.

.338 Federal

About two years after Guns and Shooting Online started promoting the .338x57 O'Connor, Federal announced the .338 Federal, a similar cartridge but based on the .308 Winchester case necked-up to accept .338" bullets. (Remember, when O'Connor proposed the .338x57 there was no .308 case, as the .308 Winchester had not yet been invented.) Apparently great minds travel similar paths!

Unlike the .338x57 O'Connor, the .338 Federal is loaded to maximum pressure with the latest (non-canister) powders to achieve the highest possible level of performance from its short action case. The .338 Federal is a rimless cartridge and uses spitzer bullets, so it is best adapted to modern single shot rifles and repeating rifles fed from box or spool type magazines. It is not intended for use in rifles with tubular magazines, such as the Marlin 336, Winchester 94 and Henry lever actions.

ATK/Federal Cartridge offers three .338 loads in their Federal Premium line and one in the Fusion line. The Premium offerings include a 180 grain Nosler AccuBond bullet at a MV of 2830 fps, a 185 grain Barnes TSX bullet at a MV of 2750 fps, and a 210 grain Nosler Partition at a MV of 2630 fps. The Fusion load drives a 200 grain spitzer bullet at a MV of 2725 fps.

.338-06 A-Square

The .338-06 started life as a wildcat based on the full length .30-06 case simply necked-up to accept .338" bullets. Premium ammo and rifle maker A-Square ushered the cartridge through the SAAMI standardization process and legitimized it in 1998, adding it to their ammunition line. Weatherby subsequently added the .338-06 to their ammunition line, and A-Square and Weatherby both offer rifles in the caliber.

The .338-06 is a powerful cartridge, using bullets of the same weight as the .35 Whelen (.35-06), but with superior sectional density and at higher pressure for increased velocity. A-Square .338-06 factory loads are available with a 200 grain Nosler Ballistic Tip bullet at a MV of 2750 fps, a 250 grain SP boat-tail at 2500 fps, and a 250 grain RN Dead Tough bullet at 2500 fps. The sole Weatherby factory load uses a 210 Nosler Partition bullet at a MV of 2750 fps.

The Comparison

As stated above, the purpose of this comparison is to see how these four cartridges relate to each other and, ultimately, how these standard .338 calibers fit into the overall scheme of things for the North American hunter. So what loads shall we compare?

The initial Hornady factory load for the .338 Marlin Express drives a new 200 grain FTX boat-tail spitzer bullet (BC .430) at a MV of 2565 fps. That will be our comparison load for the .338 Marlin.

The .338 Marlin Express is factory loaded with a 200 grain bullet, so for the .338x57 O'Connor comparison load, let's use the heavier 225 grain Hornady Spire Point (SP) bullet at 2300 fps.

In .338 Federal my factory load of choice is the 210 Nosler Partition (NP) spitzer at a MV of 2630 fps, so that is the load that will represent the .338 Federal. Coincidentally, the Weatherby factory load for the .338-06 A-Square uses that same bullet, but at a MV of 2750 fps, so that will be our representative .338-06 load.

Bullet cross-sectional area

All of our cartridges use .338" diameter bullets, and all therefore have an identical cross-sectional area of 0.0891 square inch. Bullet cross-sectional area, of course, affects the diameter of the wound channel a bullet creates as it punches through an animal and a .338 bullet creates a substantially wider path of destruction than a .30 caliber or 8mm bullet.

Sectional density

Sectional density (SD) is the ratio of a bullet's weight to the square of its diameter. The higher the SD number, the greater its length in proportion to its mass. SD is relevant because, other things being equal, a heavier bullet of a given diameter penetrates deeper than a lighter bullet of the same diameter. The more penetration a bullet achieves, the longer the wound channel it creates, until it exits the far side of the animal. SD numbers from .250 up are generally considered adequate for CXP3 game with .338 cartridges. Here are the SD numbers for our chosen bullets.

  • .338, 200 grain - SD .250
  • .338, 210 grain - SD .263
  • .338, 225 grain - SD .281

For comparison, the SD of a 150 grain .308" bullet is .226, the SD of a 165 grain .308 bullet is .248, and the SD of a 180 grain .308 bullet is .271. One of the real advantages of the .338 caliber is bullets of excellent sectional density.

Ballistic coefficient

Ballistic coefficient is calculated as the ratio of a bullet's SD to its coefficient of form. It is used to judge a bullet's drag as it flies through the atmosphere. The higher the BC, the lower the drag and the less the bullet is affected by air resistance and also crosswind. In other words, the higher the BC the more streamlined the bullet. BC has an important effect on the downrange trajectory of rifle bullets. At any given muzzle velocity, the bullet with a higher BC will shoot flatter. Here are the BC numbers of our various bullets.

  • 200 grain Hornady Flex-Tip - BC .430
  • 210 grain Nosler Partition - BC .400
  • 225 grain Hornady Spire Point - BC .397

Velocity and energy

Velocity matters because it flattens trajectory and is the major component of kinetic energy. Energy powers bullet expansion and penetration, without which there would be no killing power.

Velocity and energy figures at various ranges are published by the ammo makers for their factory loaded ammunition, and similar data is provided in the bullet maker's reloading handbooks. This makes comparing calibers and loads far more convenient than it might otherwise be! Here are the velocity (in feet per second) and kinetic energy (in foot pounds) figures for our selected loads at the muzzle, 100, 200, and 300 yards.

  • .338x57 O'Connor, 225 grain SP - 2300 fps/2640 ft. lbs. at muzzle, 2128 fps/2262 ft. lbs. at 100 yards, 1963 fps/1925 ft. lbs. at 200 yards, 1806 fps/1609 ft. lbs. at 300 yards.
  • .338 Marlin Exp., 200 grain FTX - 2565 fps/2921 ft. lbs. at muzzle, 2365 fps/2483 ft. lbs. at 100 yards, 2174 fps/2099 ft. lbs. at 200 yards, 1991 fps/1760 ft. lbs. at 300 yards.
  • .338 Federal, 210 grain NP - 2630 fps/3225 ft. lbs. at muzzle, 2415 fps/2719 ft. lbs. at 100 yards, 2211 fps/2279 ft. lbs. at 200 yards, 2016 fps/1895 ft. lbs. at 300 yards.
  • .338-06 A-Square, 210 grain NP - 2750 fps/3527 ft. lbs. at muzzle, 2526 fps/2975 ft. lbs. at 100 yards, 2312 fps/2493 ft. lbs. at 200 yards, 2109 fps/2074 ft. lbs. at 300 yards.

If around 1200 ft. lbs. of kinetic energy at bullet impact are required to humanely harvest elk, as is sometimes claimed, all of our cartridges are in pretty good shape out to 300 yards and beyond. The .338 Federal and .338-06 are loaded to much higher pressure (around 63,000 psi for the .338 Federal) than the other two cartridges, which are held to around 47,000 psi, and that is reflected here.


The distance at which a bullet drops 3" below the line of sight, when zeroed so that its maximum rise above the line of sight is limited to 3", is that load's maximum point blank range (MPBR) +/- 3". Thus a given load's maximum allowable deviation above or below the line of sight from the muzzle to its MPBR is only 3". This means that you can hold on the center of the heart/lung area of any big game animal from the muzzle out to the cartridge's MPBR without any fear of shooting over or necessity to adjust for bullet drop.

When so sighted and fired from a rifle with a scope mounted 1.5" over bore, the maximum point blank range (+/- 3") of each of our comparison loads would be as follows.

  • .338 O'Connor, 225 grain SP - 228 yards
  • .338 Marlin, 200 grain FTX - 254 yards
  • .338 Federal, 210 grain NP - 258 yards
  • .338-06 A-Square, 210 grain NP - 269 yards

Based on their trajectory, none of these are long range (approx. 300 yard MPBR) cartridges, but then they were not intended to be. On the other hand, they are far superior to traditional short range (approx. 100 yard MPBR) woods cartridges.

The .338 Marlin and .338 Federal are quite similar in MPBR and the .338-06 out-ranges the other cartridges, which comes as no surprise considering its greater powder capacity. The good news is that all of these loads shoot flat enough to be medium range (200+ yard MPBR) cartridges, and that is more than is normally required of a first rate woods or large game cartridge.

OGW killing power

Killing power is very hard to quantify due to the mass of variables, not the least of which are the game animal's state of mind when shot and the effect of bullet expansion on the wound channel. To make a complicated issue worse, most killing power formulas are devised to validate the author's point of view on the matter and have no valid correlation with broad spectrum results in the field.

In my opinion, one of the most useful attempts to estimate killing power on game animals is the "Optimum Game Weight Formula" devised by Edward A. Matunas. It at least attempts to consider more than one factor and relates the result to the live weight of the animal and the distance at which it is shot. Most of all, OGW seems to have a positive correlation with actual results in the field. (There is an extensive OGW table on the Tables, Charts and Lists Page of Guns and Shooting Online.) Here are the Optimum Game Weight results for our various loads at the muzzle, 100, 200 and 300 yards.

  • .338x57 O'Connor, 225 grain SP - 924 lbs. at muzzle, 703 lbs. at 100 yards, 528 lbs. at 200 yards, 393 lbs. at 300 yards.
  • .338 Marlin, 200 grain FTX - 1013 lbs. at muzzle, 796 lbs. at 100 yards, 621 pounds at 200 yards, 479 lbs. at 300 yards.
  • .338 Federal, 210 grain NP - 1203 lbs. at muzzle, 931 lbs. at 100 yards, 715 lbs. at 200 yards, 542 lbs. at 300 yards.
  • .338-06 A-Square, 210 grain NP - 1376 lbs. at muzzle, 1069 lbs. at 100 yards, 824 lbs. at 200 yards, 629 lbs. at 300 yards.

One wants to be careful when drawing conclusions from killing power estimates, but speaking generally we can see that as the cartridges velocity and energy increase, so does their estimated killing power. That, of course, is as it should be, since we are comparing cartridges of a single caliber.

Considering that the average male elk is estimated to weigh about 500 pounds, all of our standard .338's are satisfactory elk cartridges at medium range (200 yards). The .338 Marlin, .338 Federal and .338-06 A-Square have the power to kill elk beyond their MPBR. In practical terms, very few hunters need more rifle than this. These calibers can also serve as African medium bores, suitable for all large plains game save the dangerous CXP4 critters.


Here are the recoil energy (in foot pounds) and recoil velocity (in feet per second) figures for our comparison loads when fired in 8 pound rifles.

  • .338 O'Connor, 225 grain @ 2300 fps - 18.8 ft. lbs., 12.3 fps
  • .338 Marlin, 200 grain @ 2565 fps - 20.1 ft. lbs., 12.7 fps
  • .338 Federal, 210 grain @ 2630 fps - 22 ft. lbs., 13.3 fps
  • .338-06 A-Square, 210 grain @ 2750 - 25.2 ft. lbs., 14.2 fps

Among these calibers, only the .338x57 O'Connor comes in under the 20 ft. lb. recoil energy limit, although the .338 Marlin is very close and all can be loaded down to that level using a 200 grain bullet at a MV of approximately 2400 fps. At about 22 ft. lbs. in an 8 pound rifle (and an unseemly 25 ft. lbs. in a 7 pound Kimber 84M Classic), the .338 Federal has plenty of power at both ends. Ditto the .338 A-Square, which is even worse.


The .338x57 O'Connor is a wildcat cartridge based on a superior case that is, unfortunately, not at present in favor. To the best of my knowledge, no commercial rifle maker or ammo supplier is interested in adopting the .338x57. The introduction of the similar, but short action, .338 Federal and .338 Marlin Express effectively ended any chance the .338x57 had to become commercially viable. The .338x57 O'Connor will remain a wildcat and probably fade away, since any reloader with a .338 Federal or .338 Marlin Express rifle can duplicate .338x57 ballistics without the expense of a custom built rifle.

The .338 Marlin Express is the latest medium bore cartridge intended for use in lever action rifles. It follows in the footsteps of the .33 Winchester, .348 Winchester and .356 Winchester. Teamed with the Marlin XLR rifle, it arguably may be the best general purpose, medium bore rifle/cartridge combination offered today. (Although fans of the Browning BLR in .358 Win. caliber, and I am among them, might disagree.)

The .338 Federal is perhaps the most promising medium bore, rimless cartridge to have been introduced in decades. I am a fan of the .338 Federal, but I fear that excessive recoil will ultimately limit its popularity, just as it did the .338-06, .358 Win. and .35 Whelen before it. ATK/Federal Cartridge really needs to introduce, and promote for general use, a Low Recoil load for their .338 that duplicates the ballistics of the .338x57 O'Connor.

I read a review of the Kimber 84M/.338 Federal in Rifle Shooter magazine (published well after our far superior review, I might add), in which the author glossed over the recoil issue by describing it this way: ". . . surprisingly light recoil given the rifle's minimal heft." Translation: since all lightweight rifles chambered for powerful cartridges kick like the devil the author (an experienced shooter) wasn't surprised. Big deal! The author didn't want to admit that the .338 Federal, as factory loaded at present, is too much cartridge for such a light rifle. After all, Kimber had paid for that issue's back cover ad!

Such subterfuge may sell a few rifles and cartridges this year, but as it does the word is going to get around the shooting ranges and hunting camps that .338 Federal rifles are unpleasant to shoot. That has already happened to the .338 A-Square.

The .338-06 A-Square is an excellent medium bore cartridge, versatile and powerful. It can do more than any other standard medium bore cartridge up to the 9.3x62. (There is a comparison article featuring the .338-06, .35 Whelen, and 9.3x62 on the Rifle Cartridge Page.)

Unfortunately, since its 1998 introduction as a commercial cartridge, the .338-06 has failed to set the shooting world on fire. I am convinced that there are at least three reasons for this: 1) there are no popular priced .338-06 factory loads on the market and no popular priced rifles; 2) it kicks too hard and most hunters find it unpleasant to shoot; 3) the ballistically superior and best selling .338 Win. Mag. is far more widely available in both guns and ammunition.

Most shooters probably figure that if they need to lob 250 grain bullets at an animal and endure the consequent recoil, they might as well go for the Magnum. In addition, .338 Win. Mag. ammo is actually cheaper. Consequently, the .338 A-Square is selling poorly in Weatherby Mark V rifles.


That concludes our comparison of the standard .338 calibers. Useful cartridges they are indeed, and deserving of more support and popularity than they have generally received. I sincerely hope that the .338 Federal and the .338 Marlin Express can change that.

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Copyright 2007, 2012 by Chuck Hawks. All rights reserved.