The 9.3x66 Sako / .370 Sako Magnum

By Chuck Hawks

In 2002, Sako of Finland entered the medium bore cartridge sweepstakes with a new and sensible offering called, in European fashion, the 9.3x66. This translates to a 9.3mm (.366") diameter bullet in a case 66mm long.

In performance, the Sako cartridge is in between the standard length 9.3x62 Mauser and magnum length 9.3x64 Brenneke, which are established medium bore cartridges in Europe. Sako factory load ballistics call for a 286 grain bullet at a muzzle velocity (MV) of 2559 fps. This compares to a factory load MV of 2360 fps for the 9.3x62 and 2650-2690 fps for the 9.3x64 with the same weight bullet.

The 9.3x66 is based on a .30-06 size case with a standard .473" rim diameter and the Sako creation has an overall cartridge length of 3.34". This makes it adaptable to rifles with standard length actions. Other particulars of the new cartridge include a case length of 2.59", base diameter of .470", sharp 34-degree shoulder angle, shoulder diameter of .450" and a short .275" long neck, all features intended to maximize powder capacity. Visually, this is a modern rimless cartridge with a short neck, minimal body taper and a sharp shoulder.

The principle rationale behind the introduction of the 9.3x66 Sako is that it offers near .375 H&H Magnum performance from rifles with a standard length action. This is exactly the same rationale offered by Winchester for the introduction of the .338 Winchester Magnum back in 1958, by Norma for the introduction of the .358 Norma Magnum in 1959, by Steyr/Hornady for the .376 Steyr in 2000 and by Ruger for the introduction of the .375 Ruger in 2007. All of these cartridges deliver similar levels of performance. They also deliver similar levels of recoil, which is to say considerable.

Sako claims that the 9.3x66's .473" rim diameter allows a 5-shot magazine capacity, just like the 9.3x62mm. This is one cartridge more than most rifles chambered for belted cartridges, which have a .532" rim diameter. That is a valid point, but perhaps not enough to overcome the popularity and worldwide distribution of .338 Winchester Magnum rifles and cartridges. Or the fact that a belted case provides positive headspacing, no matter how small the shoulder or hard a rifle's firing pin blow may be.

Although I have read that it is selling moderately well in Europe, thus far Sako has not seen fit to offer 9.3x66 ammunition in the U.S. Instead, Sako officials asked Federal Cartridge to develop American loads for the 9.3x66. Federal complied and in 2008 introduced their ".370 Sako Magnum" loads for the cartridge.

Federal's nomenclature for their 9.3x66 loads is deceptive, since it is exactly the same cartridge and does not use .370" diameter bullets. It retains .366" (9.3mm) diameter bullets and the Federal .370 Sako Magnum is completely interchangeable with the European 9.3x66 Sako. Furthermore, it is not a "magnum" cartridge in length or diameter. It is not based on a magnum case, but rather on a necked-up .30-06, the most "standard" rifle cartridge in the world!

Nomenclature aside, the Federal Premium Cape-Shok .370 Mag. factory loads for the 9.3x66 Sako are indeed powerful and Federal recommends them as suitable for CXP4 game. They launch 286 grain Nosler Partition or Barnes TSX bullets (SD .305) at a MV of 2550 fps and ME of 4130 ft. lbs. At 200 yards the numbers for the TSX bullet are 2190 fps and 3045 ft. lbs. Here is the trajectory of that load when fired from a scoped rifle: +1.2" at 50 yards, +2.4" at 100 yards, 0 at 200 yards, -9.6" at 300 yards, -27.5" at 400 yards. These ballistics were derived in a 24" test barrel.

I have read in the print media that the 9.3x66/.370 Sako kills like a .375 H&H, but kicks more like a .35 Whelen. In fact, I seem to have read the same general thing about every similar medium bore cartridge to be introduced in my lifetime. I wonder if gun writers will ever tire of this cliche? The 9.33x66 is a powerful medium bore cartridge and all such cartridges kick hard in the real world, if not in the alternative universe of gun magazines. The recoil calculator estimates that to drive a 286 grain bullet to a MV of 2550 fps from an 8.5-9 pound rifle, the 9.3x66 is going to paste the shooter with 35-36 ft. lbs. of recoil energy. Compared to the 20 ft. lbs. of recoil that most authorities figure is the maximum most of us real world shooters can tolerate, that's a lot of kick! If you were wondering, the .375 H&H (300 at 2530 fps) fired in a 9 pound rifle delivers about 37 ft. lbs. of recoil energy and the .35 Whelen (250 at 2400 fps) fired in an 8.5 pound rifle delivers about 24 ft. lbs. The bottom line is that the .370 Sako is close to the .375 in power and recoil. It could be no other way; the laws of physics are immutable.

Frankly, the market for powerful medium bore cartridges is quite limited in North America and there are already too many cartridges vying for a share of this small market. Among "standard length" magnums, the .338 Win. Mag. is the outstanding success story, because it has proven ideal for elk, moose, the great bears and similar size game worldwide. The .358 Norma Magnum is based on the .338 Mag. case necked-up to accept a .358" bullet and the .375 Ruger is based on a non-belted rimless case with the same .532" magnum rim diameter. For those who want a standard .30-06 diameter cartridge, the very niche for which the 9.3x66/.370 Magnum was designed, we already have the .338-06 A-Square, .35 Whelen and .9.3x62. The .350 Remington Magnum delivers similar performance and fills the bill for those who favor short action rifles. Of course, there are several cartridges available for rifles with long actions, including the .340 Weatherby, 9.3x64, .375 Weatherby and the grand daddy of them all, the .375 H&H Magnum. Single shots, doubles and drillings can be had in 9.3x74R and .375 H&H Flanged, among others. It is therefore somewhat hard to imagine the 9.3x66/.370 Magnum catching on in a big way in the overcrowded U.S. market.

None of the major U.S. reloading manuals include the 9.3x66mm/.370 Sako, as I write this in early 2009, so trustworthy reloading data is hard to come by. If I were developing loads for a 9.3x66 rifle, I'd probably start with recommended 9.3x62mm loads and work up from there, chronographing and watching carefully for signs of excess pressure as I went.

Note that the Sako and Federal factory loads use advanced technology powders not available to reloaders, so it will probably not be possible to duplicate factory load velocities at home. I would estimate that velocities of 2400-2450 fps with a 286 grain bullet will be the maximum attainable within permissible pressure limits using canister powders.

Given the decades of practical experience recorded with the 9.3x62, 9.3x64, 9.3x74R, .358 Norma Magnum, .338 Winchester Magnum and limited experience with the more recent .376 Steyr, it is easy to predict that the 9.3x66/.370 Mag. will be a very fine "stopper" for the largest and most dangerous CXP3 size game, including lion and the great bears. It would, of course, do a bang-up job on the largest North American game including moose, musk ox and bison.

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Copyright 2005, 2012 by Chuck Hawks. All rights reserved.