The 9.3mm-338 Magnum Wildcat

By Chuck Hawks

This rather obscure wildcat cartridge is created by necking-up .338 Winchester Magnum brass to accept 9.3mm (.366") bullets. No other case modifications are required. The resulting cartridge is very similar to the .358 Norma Magnum, but presumably appeals to European hunters who are more familiar with the various 9.3mm medium bore cartridges than .35 caliber (9mm) rifle cartridges.

Although based on a different case, the performance of the 9.3-338 Magnum is also comparable to that of the German 9.3x64mm Brenneke. This magnum class 9.3mm cartridge was designed around 1910 and commercial ammunition and rifles are still available in Europe and, to a limited extent in North America, although it has never been very popular.

Like any wildcat, the 9.3mm-338 also appeals to shooters who simply want something different. The 9.3-338 Magnum easily satisfies the latter desire without being difficult to form. Redding, I believe, can supply reloading dies for the caliber.

Since the 9.3-338 is so similar to the .358 Norma Magnum in terms of ballistics, purpose and capability, it is unlikely that the 9.3-338 will ever catch on in a big way. Particularly since the .358 Norma has never caught on, even though factory loaded ammunition is available from Norma and commercial rifles have been produced in the caliber.

The reason for the commercial failure of the .358 Norma Magnum and the 9.3x64 Brenneke is, in a word, recoil. They simply kick too hard for most shooters to endure. Unfortunately, the 9.3-338 Magnum kicks equally hard with bullets of similar weight. However, for those who can stand the kick, it is a very effective cartridge for dangerous and outsize game.

9.3mm bullets are not terribly common, but they are available from A-Square, Barnes, Nosler, Speer, Swift, and Woodleigh among others. The most common weights are 250 grain (SD .267), 270 grain (SD .288), and 286 grain (SD .305). The latter is the most popular weight for Europeans taking their 9.3s to Africa.

I have no reloading data for the 9.3-338, but it should offer performance virtually identical to the .358 Norma Mag. with bullets of similar weight, since both are based on a necked-up .338 Win. Mag. case and there is only .008" difference in bullet diameter. If I were developing loads for a 9.3-338 rifle I would probably start with 250 grain bullets and the beginning loads listed for the .358 Norma. The 9.3-338 should actually develop very slightly less pressure with any given load due to its slightly larger bullet diameter. Chronograph all loads and work up slowly, keeping a sharp eye out for any sign of excess pressure.

The Speer Reloading Manual Number 13 lists loads for the .358 Norma with muzzle velocities (MV) from about 2400 fps to 2732 fps with their 250 grain bullets. IMR 4350 is considered a good powder for the .358 Norma and yielded the top velocities, but loads using IMR 4320, IMR 4064, IMR 4895, and H380 are also listed. The same powders should work in the 9.3-338.

The Nosler Reloading Guide, Fifth Edition lists loads for the 9.3x64 Bernneke using their 250 and 286 grain bullets. Since the 9.3x64 is similar in configuration to the 9.3-338 wildcat, but has slightly less case capacity, starting loads for the 9.3x64 should also be applicable to the 9.3-338. Again, work up slowly, chronographing as you go, and check carefully for any signs of excessive pressure.

Nosler quotes MV's for the 9.3x64 and their 250 grain Ballistic Tip bullet that are similar to those listed by Speer for the .358 Norma with their 250 grain bullets, but top out at 2802 fps, which is a reassuring sign. For their 286 grain Partition bullet in the 9.3x64, Nosler quotes MVs ranging from about 2400 fps to 2690. (I suspect that Nosler lists loads at somewhat higher pressures than does Speer.) Once again, IMR 4350 yielded the best velocities, another good sign.

Nosler reported top accuracy in their 9.3x64 test rifle using RL-15 powder with both bullet weights, and also listed loads using Viht N140. Both reloading manuals list loads for IMR 4350 and IMR 4895 powders, however, so those are the powders with which I would be inclined to start load development.

I believe that similar maximum velocities to those mentioned above can be attained in the 9.3-338 with 250 and 286 grain bullets. Drive a 250 grain bullet at a MV of 2700 fps and you are looking at muzzle energy (ME) of 4048 ft. lbs. Back the velocity off to 2600 fps and you are still looking at 3752 ft. lbs. That should be excellent medicine for large North American game, including Alaskan moose and the great bears. Ditto for African lion and the largest African antelope.

Drive a 286 grain bullet at a MV of 2600 fps and the ME is 4294 ft. lbs. Reduce the MV to 2500 fps and the ME is 3970 ft. lbs. Surely those loads, with bullets of appropriate design, should be adequate for practically any purpose for which any medium bore rifle and cartridge are suited.

Any advantage the 9.3-338 Magnum has over the .358 Norma or 9.3x64 Brenneke is pretty questionable, and for that matter any advantage over the parent .338 Winchester Magnum is debatable. They all use bullets of similar weight and are based on cases of similar capacity.

However, there is also no doubt that the 9.3-338 is a very powerful medium bore cartridge. It is easy to form from widely available brass, and in North America it is probably easier for a reloader to reform .338 Win. brass than to purchase 9.3x64 brass to reload. The 9.3-338 Magnum is a good choice for the hunter/reloader who cannot live without a 9.3mm wildcat.

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Copyright 2005, 2014 by Chuck Hawks. All rights reserved.