These days, this is an obscure cartridge in North America, and not particularly popular anywhere else. In appearance it looks very much like the 338 Winchester Magnum, but a closer look will reveal that the bullet is fatter. In fact, the 358 Norma Magnum is almost exactly like what a 35-caliber cartridge based on the 338 Win Mag case would be. Even so, there are enough slight differences to keep one case from being used for the other cartridge, sized either up or down.
Few models of rifles have been chambered for the 358 Norma Magnum, so I asked Ed Brown to build a pair for me. I first became familiar with the round in the late '60s or early '70s, having the opportunity to shoot one built on a commercial FN Mauser action. The difference in smack over a 30-caliber magnum, while at the range with a backstop wet from rain the day before, was impressive. The 30 was making a good "thud," but the 358 NM was making a hell of a whack and throwing mud all over the place.
The Ed Brown rifles are identical, with sequential serial numbers. They have stainless Pac-Nor barrels of No. 4 contour (magnum hunting) with 12 twist, and when test fired at Brown's facility they each went sub-moa with factory ammunition. One of the problems with 35-caliber cartridges of the large variety is the limited available selection of bullets. This affects loading for the 358 STA in the same way as the 358 NM. There are some excellent Woodleigh bullets available, as well as those dandy Swift A-Frames in 225, 250, and 280 grains, but not much else for hunting the heavy game for which the round is intended. On the plus side, Hornady makes a darn good 250-grain InterLock in both Spire Point and Round Nose, both of which shoot well and will handle all but the toughest game. Further on the plus side, as many 35-caliber rifle shooters know, 0.357- and 0.358-inch-diameter handgun bullets may be used for practice and in very light loads for "finishing" big game. Creating such loads takes plenty of beforehand study and care, so we're not going to get into the particulars here.
For all of its nasty knockdown power, the 358 NM doesn't kick too bad. It's very much like the 338 Win Mag in that department, but the increased 20 thousands bullet diameter is said to physically make a difference on the well-being of animals who might not like you. That being said, I would choose the 358 over a 338 when venturing into brown bear country. Actually, something bigger yet makes more sense if you're tugging your way through thick brush, and find yourself 35 feet from an ill-tempered bear that's been carrying around the bullet from a 30-30 for the past week.
Cartridges in the light-heavyweight category are the favorite of many stand-up-kind-of-guy hunters. They realize that they probably won't fire the rifle much more than 20 round a year, so recoil isn't an important subject to them. There's a great deal of satisfaction in owning a high-performance rifle, even if you aren't going to use it all that much. There's also a great deal of satisfaction in owning an M-Class BMW or an AMG Mercedes Benz, even if all you do with it is tool along with the normal flow of traffic. Smug can be a good thing.
One other plus with the 358 NM is that it performs well with several popular powders over a fairly wide burning rate. That somewhat larger bore removes a lot of the finicky fuss displayed by many magnums, and also helps it to achieve a full measure of velocity with no more than a 24-inch barrel. All in all, the 358 Norma Magnum is just a whisker behind the 375 H&H Magnum in power, and somewhat more pleasant to shoot. Although there is little place for it in this world, as it does not qualify as a dangerous game round for Africa, I think it's a dandy.