Sometime after World War II Jack O'Connor, the Dean of American gun writers, proposed a new .33 caliber cartridge. He wanted to drive a 200 grain flat point or round nose bullet at a muzzle velocity (MV) of 2400-2450 fps. He felt that this would make an excellent brush cartridge for the deer and black bear hunter, particularly if available in a repeating rifle that offered quick follow-up shots.

O'Connor had done a series of brush penetration tests and discovered that the .348 Winchester performed well, but kicked pretty hard for a deer cartridge. O'Connor's concept was a medium bore cartridge with moderate recoil that the average woods and brush hunter could use for shooting deer, feral hogs, black bear, and possibly elk.

As I related in my article "Woods and Brush Rifles," O'Connor theorized that such a cartridge should be able to drive its bullet through the brush better than the 30-30, .307 Winchester, .308 Marlin, .300 Savage and .308 Winchester, open up fast, and would have more shocking power than the .35 Remington or .38-55. The trajectory should be flat enough to allow a point blank range in excess of 200 yards. If the new cartridge's recoil could be kept below 20 ft. lbs. the average deer hunter could take advantage of its benefits.

This was before the advent of the .308 Winchester case, so O'Connor suggested that the new cartridge could use a necked-up 7x57 case. A few years later Winchester introduced the .358 Winchester on a necked-up .308 case, but loaded it to a maximum average pressure (MAP) of 52,000 cup in order to duplicate the performance of the earlier .348 Win. The result was a medium bore elk cartridge that kicked about as hard as the .348 and likewise failed to catch on with the average woods hunter. Winchester later repeated their error when they introduced the .356 Winchester, a rimmed version of the .358 for the Model 94 Big Bore rifle, also loaded to a MAP of 52,000 cup in order to maximize ballistic performance, with a similar lack of success.

I thought O'Connor's concept was worth pursuing, and I wrote about it in several articles, including my rather detailed piece "New Woods Cartridge: The .338x57 O'Connor," which you can find on the Rifle Information Page. These articles generated considerable interest among Guns and Shooting readers, but the cartridge was not picked-up by a major ammo manufacturer, at least in its original form.

However, for 2006 Federal Cartridge announced the introduction of their .338 Federal, based on the .308 Winchester case necked up to accept .338" diameter bullets. This cartridge is conceptually very similar to the .338 O'Connor but, like Winchester, Federal could not resist the temptation to load to maximum pressure to achieve maximum velocity, thus repeating the mistake made with the .358 Win.

The .338 Federal drives a 210 grain bullet at a MV of 2630 fps. It is an excellent cartridge, and we have written about it extensively on Guns and Shooting Online. The reloader can easily reduce the powder charge to achieve O'Connor's ideal muzzle velocity of 2400-2450 fps. But for the woods and brush country deer hunter who doesn't reload, the .338 Federal is no better than the earlier .348 and .358 in terms of recoil.

The 2007 introduction of the .308 Marlin Express, the result of a joint effort by Hornady and Marlin, brought forth a new case that could be adapted to a .338 O'Connor type cartridge. This possibility was brought to my attention by Guns and Shooting Online reader Jon Huffman. With about 10% less case capacity that the .338 Federal, perhaps Hornady and Marlin could be persuaded to offer a medium bore cartridge (a ".338 Marlin Express") that holds MV to 2400-2450 fps with a 200 grain bullet and recoil to the 20 ft. lb. limit envisioned by Jack O'Connor. And what better vehicle for such a cartridge than the fast handling Marlin 336XLR lever action rifle? Certainly a .338 wildcat based on the .308 Marlin case is likely, almost inevitable, when .308 Marlin brass becomes available.

The barrel of a .338 Marlin Express rifle should have a bore diameter of .330 inch and a groove diameter of .338 inch. It should be rifled with 6 grooves, right hand twist, as is customary for modern .338 barrels. The rifling twist for almost all modern .338 cartridges is 1 turn in 10 inches, which should also be suitable for the .338 Marlin, although a 1 in 12 twist would probably also work well.

When developing the .338 Marlin Express it should be remembered that the primary goal is an effective woods cartridge that kicks less than previous medium bore cartridges such as the .338 Federal, .338-06 A-Square, .348 Winchester, .35 Whelen, and .358 Winchester. And it must outperform such old standbys as the .30-30 Winchester, .32 Win. Special and .35 Remington.

I am convinced that the lack of popularity and commercial success of the previously mentioned medium bore cartridges is directly attributable to their recoil, which is greater than most shooters are willing to tolerate in a woods rifle of reasonable weight. In the .338 Marlin Express, deer and black bear loads that exceed 20 ft. lbs. of recoil with a 200 grain bullet would defeat the primary purpose of the cartridge.

Working with their powder supplier, Hornady has achieved superior efficiency with the .308 Marlin, holding the MAP to the mid-40K range. Hopefully, similar powder technology can be applied to the development of a 200 grain/2400 fps load for the .338 Marlin.

Obviously, to develop loads we must select appropriate bullets. Until quite recently, Hornady offered a 200 grain flat point Interlock bullet (#3315) that would be excellent for the proposed .338 Marlin. This bullet has been discontinued, but I see no reason why it could not be reintroduced (perhaps with a slightly revised jacket profile) for the new cartridge. A flat point bullet is ideal for a woods/brush cartridge.

This new .338 Marlin Express load should be part of the more or less popularly priced Hornady Custom Rifle line. There is no need, at least initially, for the premium "LEVERevolution" treatment. (Although, it would be nice in addition to a standard priced load!)

The 200 grain Hornady FP (SD .250) at a MV of 2400 fps has muzzle energy (ME) of 2558 ft. lbs. At 100 yards the velocity is 1996 fps and the energy is 1770 ft. lbs. At 200 yards the velocity is 1638 fps and the energy is 1191 ft. lbs. At 250 yards the velocity is 1507 fps and the energy is 1008 ft. lbs. And at 300 yards the velocity is 1368 fps and the energy is down to 831 fps, about the minimum recommended for deer hunting. So, in terms of killing power, the .338 Marlin Express is a 300 yard deer cartridge with the Hornady 200 grain flat point bullet. Its practical effective range would be limited by its trajectory.

The trajectory of the 200 grain FP bullet at 2400 fps, assuming a scope mounted 1.5 inches over the bore, is as follows: +1.6 inches at 50 yards, +2.9 inches at 100 yards, +2.1 inches at 150 yards, 0 at 185 yards, -3 inches at 214 yards, and -7.9 inches at 250 yards. So zeroed, the maximum point blank range (MPBR) of this load is 214 yards (+/- 3 inches).

The theoretical killing power of the .338 Marlin looks pretty good. The optimal game weight for the 200 grain Hornady flat point bullet at a MV of 2400 fps is 253 pounds at 215 yards, 368 pounds at 150 yards, and 487 pounds at 100 yards. As anticipated, that should be a very effective deer, boar, and black bear load.

The trajectory and killing power are excellent for our purposes, but what about recoil? I ran the (estimated) numbers and found that a .338 Marlin rifle weighing 8 pounds and shooting a 200 grain bullet at a MV of 2400 fps should generate about 19 ft. lbs. of free recoil energy. Voila!

In the future, Hornady could design a new bullet, perhaps 180 grains (SD .225), using their Flex Tip technology. This could be driven to a somewhat higher velocity for those who desire a flatter trajectory, while still remaining within the 20 ft. lb. recoil limit. Such a load might extend the MPBR to around 250 yards.

The above figures demonstrate that Jack O'Connor's original concept was perfectly valid. The recoil of our .338 Marlin Express should be less than the 20.4 ft. lbs. of recoil attributed to an 8 pound .308 Winchester rifle shooting a 200 grain bullet. A practical medium bore caliber that kicks no more than a popular small bore!

Note: This article is mirrored on the Member Side Wildcat Cartridge Page.