Sako Calibers

Sako is the only factory that manufactures both firearms and cartridges. Over the years, Sako has developed two proprietary calibers bearing the Sako name. Representing the extremes of the spectrum are the 7x33 Sako, originating from the early years, and the 9.3x66 Sako, productized under Beretta's ownership of Sako, also known as the .370 Sako Magnum.

7x33 Sako

​It was 1942 when the relatively new company Sako sought more business. The first, somewhat hidden, internally developed elegant rifle, the L42, emerges and, through several intermediate stages, becomes a decent export product, reaching even to a new continent. L42 and its improved version, the L46, laid the foundation for Sako's commendable firearm production. However, its peculiar caliber didn't sell well in the larger world, as it was a local oddity; the 7x33 Sako was designed to be manufactured on Sako's machines.

​Thus, the birth year of the cartridge is the same as that of the successful proprietary rifle production that began the success story.

To understand the product, one must know the trends of the time. In the early 20th century, the 7 mm caliber was popular. This was partially because the 7.62 caliber was prohibited, so the Mosin-Nagant-based "pystykorva," aka "Spitz" rifles wouldn't wear out. Sako had ready machinery for producing 9mm Luger cartridges, making nearly 300 million pistol and submachinegun cartridges between 1941 and 1945.

​When experimenting with how much a cartridge case could be stretched, it was found that 33mm could still be reliably managed. Typically, rifle cases were larger than this, like the typical 7x57; thus, the bullets were heavier. A heavy bullet wasn't suitable for a small case and a slow twist rate, so a suitable lightweight bullet was produced using the existing machinery. Therefore, by combining these two characteristics, they ended up with the bottlenecked 7x33 caliber, where the nominal length of the case is 33.3mm.

​In 1942, a batch of 100,000 cases was made, and one of the field researchers was, among others, the true hunting and shooting legend Tauno V. Mäki, testing the capabilities of the new caliber. However, it wasn't until 1946 that the cartridges arrived in stores, as there was an advertisement in the Finnish Metsästys & Kalastus magazine in October stating that they would soon be available. In the November issue, it was announced that they were now available.

​The cartridge's overall length is 44.4 mm, with a base diameter of 10 mm. It fits perfectly into the slim L42 and L46 rifles. Likewise, it suited its intended purpose, namely the thinning of the abundant capercaillie and black grouse populations, as the slow velocity of the bullet did not spoil the meat. Of course, for the same reasons, it still works excellently for all kinds of small game. Compared to more modern cartridges, the only drawback is the fairly curved trajectory of the round-nosed bullet, which emphasizes the need for accurate distance estimation. However, at that time, open sights were primarily used in the field, so long-range precision shooting was not practiced.

​Initially, the weight of the bullet was 6.0 grams, but it soon stabilized at 5.1 grams. In the early brochures, a velocity of 725 m/s at a distance of 25 m was promised, meaning a muzzle velocity of about 775 m/s was calculated using the Norma ballistic program. In the latest Sako cartridge table, the same 5.1 g bullet is listed with a muzzle velocity of 750 m/s and a velocity of 568 m/s at a distance of 100 meters, with a corresponding kinetic energy of 823 joules. If the rifle is zeroed for a distance of 150 meters, the bullet will be 5.6 cm high at 100 meters and will drop by 16.3 cm at 200 meters. This is primarily influenced by the bullet's poor ballistic coefficient, which is only 0.147.

​The cartridge meets the minimum requirements of Class 2 for bullet weight exceeding 3.2 grams and kinetic energy exceeding 800 joules (at 100 meters), allowing it to be used for hunting roe deer, wolf, lynx, wolverine, beaver, mouflon, seal, and smaller game. Available bullets include full-metal-jacketed Speedhead 108B and the expanding bullet Gamehead 109B.

If one wishes to compare the 7x33, similar in length are cartridges such as 25-20 Win, 22 Hornet, and 218 Bee, all of which were chambered in the L46; newer ones like the 357 Magnum are approximately the same length. An interesting comparison is the recently popularized AR customized .300 AAC Blackout (7.62x35), with a base diameter of 9.6 mm and a case length of 35 mm. Much time has passed, yet we have circled back to a similar situation as Sako did almost 80 years ago.

​If a broader range of bullets were available, the Sako caliber would be excellent for reloading. A wide range of 7 mm bullets is available for various uses, but they are intended for larger cases and typically start from 6.5 grams and above. The challenge is that the bullets are long, so the slow twist rate no longer stabilizes them.

​A small case consumes little powder, keeping costs low, and using low-pressure cases ensures a long service life. The primer is a small rifle primer. With low temperatures and minimal powder charge, the barrel will last indefinitely.

Finding reloading data is more challenging; the only sources found are older editions of Hyytinen's "Jälleenlataajan Käsikirja" and Vihtavuori's older editions of the "Reloading Manual," which include data for both N110 and N120 powders; Hyytinen's book also provides data for N340 powder. Likely, Paananen's book also covers the caliber, but its high price has deterred purchase. The maximum velocity achieved is 800 m/s with a charge of 1.36 g of N120 powder. The allowed pressure is exceptionally low by modern standards at 2800 bar.

Shell holders are available, although they are significantly more expensive than those for common calibers. However, availability itself is not a limiting factor. If one engages in bullet casting, this would be an excellent caliber for loading with cast bullets.

On the Range

Naturally, the Finnish milestone had to be test-fired, and what better way than with the original model of the L46, manufactured at the beginning of 1949, featuring a birch stock and side-mounted safety, similar to the Mauser design.

Sako rifles come with excellent open sights, but due to aging eyesight, it was decided to use optics. The original Sako mounts were too low for the bolt handle's movement, so a small scope was mounted on the front base using a dovetail/Weaver adapter.

The precision promise made by Sako for their combination was considerable; the factory ammunition guaranteed 40 mm at 100 meters! And unlike many modern manufacturers who test with only three shots, Sako's guarantee was based on a whopping 10-shot group. This number of shots fairly represents the true accuracy achievable with the rifle-ammunition combination. The Lokomo steel barrel was highly regarded, and the rifling produced by cutting was top-notch.

Now, on the 100-meter outdoor range, despite considerable wind, the results were surprisingly good. As we know, a slow bullet is sensitive to wind. With full-metal-jacketed bullets, the five-shot groups were 34 and 37 mm, while with soft-point bullets, they were 26 and 36 mm. At least this rifle and these cartridges couldn't have been returned to the factory for violating the tight precision guarantee.

Velocity measurements were taken 10 meters from the muzzle using Sako's loading room's accurate gauges. For full-metal-jacketed bullets, a 10-shot series yielded an average velocity of 740.5 m/s, with a slight variation of 13 m/s. Similarly, the normal variation in velocity was an excellent 4.5 m/s.

Based on the manufacturer's stated form factor and calculated using the Norma app, this should correspond to an impressive 760 m/s muzzle velocity. On the range, our meter gave a value of 767 m/s when fired from the test rifle, so the results were quite close to that.

Thus, the old classic is suitable in all respects, also in terms of actual measurement results, for small game hunting. Shooting is very low-recoil and enjoyable, and the muzzle blast doesn't come close to the noise of magnum calibers.

Sako has discontinued the production of these cartridges several times and restarted it at the public's request. The latest production restart was ten years ago when customers in Norway, Sweden, and Finland inquired about cartridge availability.

However, those needing this caliber shouldn't delay their purchase decision, as it is, in any case, a marginal cartridge sold in small quantities. Since Sako no longer manufactures 9mm Luger cartridges, the cartridge case material has also changed to rifle cartridge cases.

The packaging for 7x33 Sako now comes in a 50-piece bulk box instead of the previous single-pack box.

9,3 x 66 Sako

​As indicated, Sako's larger caliber is intended for big game hunting. Here in Finland, it's primarily for moose and bears, although it's also suitable for deer. Initially, it offered an option for those heading to Africa, ideal for taking down even dangerous large game.

Sako introduced a range of loads alongside the cartridge's release, including the 18.5g Ramhead loaded with Barnes solid bullets. Federal, another producer of this caliber, still offers a similar option, labeled .370 Sako Magnum, known as such in America. Their Safari series offers two options: Woodleigh Hydro Solid and Swift A-Frame, both weighing 18.5g. These two will handle almost anything.

Sako describes the caliber as a "Medium Big Game Magnum," indicating it's suitable for medium to large-sized game.

The development of this novelty took just over a year, with the dimensional drawings dated February 16, 2001, hitting the shelves in July of the following year. However, it was based on the 9.3x66 EK wildcat cartridge; enthusiasts will surely recognize the significance of the letters.

The process was similar to the previous one: stretch an existing cartridge case as long as possible. This time, the starting point was the 9.3x62, the favorite of German elk hunters dating back to 1905. Its 62mm case was stretched by 4mm, increasing the powder capacity by 10%. This was measured using Sako cases filled up to the neck. By raising the allowed pressure from the original 3900 bar to the current standard of 4150 bar and using high-energy powder, the resulting performance approached the .375 H&H Magnum. The values ​​are also close to Wilhelm Brenneke's 9.3x64, developed in 1930, with its thick-walled cartridge, and significantly more potent than the popular 9.3x74R. An excellent feature is that the cartridge chamber can be made with the tooling for the 9.3x62 just by sinking it 4mm deeper.

Increasing the velocity from 710 m/s to 765 m/s for the 9.3 x 62 typically adds terminal energy to an 18.5g bullet and makes its trajectory flatter. Of course, the trade-off is increased recoil, although, in this case, not excessively so. According to the laws of physics, a more powerful caliber will have more recoil. However, tolerance to recoil is highly individual, so making a general statement about it is challenging. During testing, the recoil didn't feel excessive. With a lightweight Sako rifle without a muzzle brake, a test series of 3+3 on a moose target yielded over 50 points on the first try. If recoil is a concern, a muzzle brake or, increasingly popular nowadays, a suppressor is an even better option. A rifle equipped in this way will have less recoil and make less noise.

With the introduction of the new caliber, Sako also launched a complete range of factory-loaded cartridges. There was an option tailored to every need, totaling four types of cartridges. Alongside the new caliber, a new big game bullet, the 18.5g Hammerhead, was developed. This round-nosed soft-point bullet features a bonded core and jacket, with the jacket thickening noticeably towards the rear. When test-fired into wet paper and wet clay, the bullets mushroomed beautifully. It's a suitable choice for traditional moose and bear hunting.

Another option was the 18.5g Powerhead, which penetrates deeper than its equivalents. It features the well-known, all-copper Barnes-X bullet.

The third option offered excellent ballistics: the 16.2g Arrowhead, featuring Nosler's Ballistic Tip. Its good flight characteristics are due to its wedge-shaped tip and boat tail. The thin-jacketed bullet opens rapidly upon impact, making it ideal for thin-skinned big game. Due to its flat trajectory and significant shock effect, it was a good choice for long-range shooting. Sako no longer loads this bullet.

Lastly, the true dangerous game bullet was the 18.5g Ramhead. Again, Barnes manufactured the bullet, but this time, it was a Solid, made of solid brass. This round-nosed and non-expanding bullet offers the best possible penetration, a feature necessary when shooting from the front or rear sectors, where the expanding bullet's penetration isn't sufficient. It's a good option for thick-skinned and dangerous game in Africa. Sako no longer loads this bullet, either. Instead, two additional products have been added to the production line: Sako's own all-copper big game bullet, the 14.9g Powerhead Blade, and the full-jacketed lightweight 15g Speedhead.

Regarding dimensions, it's positive that the maximum length for the 9.3 x 66 Sako cartridge is 85mm, allowing for using a standard Sako bolt, the same one used, for example, in the .30-06. Powerful magnums usually require a long action, which makes the rifle heavier and more cumbersome.

Is the new caliber better than its predecessor? Factually speaking, yes, it clearly is. This is a genuinely versatile caliber for big game hunting. Unfortunately, there are already plenty of calibers available, with many being similar or identical for almost every purpose. In light of this, it requires belief to introduce something new to the market, but many manufacturers have done so in recent years. If the 9.3 x 62 didn't already exist, the 9.3 x 66 Sako would likely be a success. Not many manufacturers have started producing rifles and cartridges for a new caliber. In any case, it's a commendable move by Sako, which also improves the company's image.

Other Interesting Facts:

Over time, Sako has also been involved in developing other cartridges. The legendary long-range favorite, the .338 Lapua Magnum, was developed by Lapua with contributions from Sako and Accuracy International. However, both were more involved in the rifle side, as they produce two of the top rifles in their field, which many countries have chosen as their official sniper rifles.

Similarly, the small but neat .338 Federal, created by modifying the basic case of the .308 Winchester and first introduced at the 2006 trade shows, originated from Sako's drawing board. Sako defined the maximum pressure and sought functional loads. This excellent medium-range deer cartridge could very well, and perhaps even more justifiably, be named the .338 Sako. However, since Federal didn't have a rifle cartridge bearing its name, only a revolver cartridge, the .327 Federal Magnum, so...