370 Sako Mag (9.3x66)

[fsrmg1]

Does anyone have any experience with the 370 Sako Mag, also called the 9.3x66mm? I've seen some Sako ad's listing that caliber, but haven't heard or seen much else. I contacted Sako about it, and they told me that it was developed for the Nordic countries to use on the big bears and elk (moose).

They said it was basically a 9.3x62mm lengthened to as long that would fit in a standard '06 type action. They even sent me the case and chamber dimension diagrams to compare with the 9.3x62mm . Sure enough everything is the same, just 4mm longer to the shoulder.

They also said something about it having a slightly higher operating pressure than the 9.3x62mm, about like that of a 308 or typical belted magnum. They also said that this and through the use of newer triple based high energy powders, they can get close to 375 H&H performance out of it. Of course by doing the same with the 375, they could increase it as well.

Does anyone have any experience with this cartridge? How does it perform? I like the idea of 5 of those in a standard action.

 

[Odinsraven]

Nope but there is already the 9.3x62 9.3x64 and 9.3x68. ... why springs to mind as the 64 I believe is almost .375 power ....

 

[Witold Krzyżanowski]

I think the same as Odinsraven.
Witold

 

[Red Leg]

Can add the .376 Steyr to that list of near twins as well.

 

[Odinsraven]

Ok guys how about this the 12.7 x 108 necked down to 9.3mm. Might just fit in a long action magnum rifle .......

Back of a beermat calculations suggest that it would have a case capacity of 300 gr h2o ......would start to make the current 9.3 offerings seem a little weak and indeed underpowered .........Ohh well another one for the file .....

 

[Spooksar]

I used mine in Namibia this year it worked well. I had to do a very quick load development. Ended up using Reloader 19 for 2700 fps with a 250 gr Accubond.

 

[fsrmg1]

I wonder if it would be worth the effort of rechamber a 9.3x62mm to the .370 Sako for a performance boost? I think the gap is about an extra 200 fps with factory ammo and maybe half that with handloads using the same same powder type loaded to equal pressures.

I guess the down side is scarcity of loaded ammo and brass. I load my own anyway and the 9.3x62mm is not exactly a common calibre either, but still locatable if you look around.

 

[fsrmg1]

Just a fellow up, I ended up converting my FN M98 from 9.3x62 to 9.3x66 and am happy with the results.

The 62's bore had a very light frosty pitting when I got it, but was still strong. The rifle shot good, but fouled quickly and collected copper like I've never seen before. I sorted this out with a good fire lapping, which left the barrel nice and smooth/shiny. I could really feel the difference when pushing a patch through the bore, no more dragging. Anyway, this left the chamber throat looking a bit more worn than I liked, so here is where the longer 66 chamber come in to play.

Due to the barrel band rear sight/recoil lug arrangement, along with barrel to stock contour, I simply didn't want to turn the barrel back a couple-few threads to clean the throat and keep it a 62. She just wouldn't look right that way...

The head, neck and shoulder of the 62 and 66 are the same, it is only the body of the 66 is longer. This easily allowed the chamber to be recut and moving the throat 4mm further up the barrel. Once done, the throat was nice, sharp and crisp again.

Time to go shooting! I located about 250 unprimed Sako cases and loaded them up using 62 data. They fired perfectly, didn't foul up as before and the accuracy after a few shots was more consistent. 100m groups went from close to 2", down to about 1.1". Having substantially less copper fouling, the barrel was much quicker and easy to clean as well. A great time saver for me!

One thing I did notice is that I couldn't get all 5 rounds in, only 4, with the last being very tight. I looked at the action magazine walls and noticed that the recess was cut for the 62 shoulder length, so the longer shouldered 66 case wasn't sitting flush with the upper magazine side walls. This was easily cured by using a Dremol to move the recesses forward enouph to allow the 66 case to sit flush, followed by a good polish to clean things up. I also used this opportunity to clean up and polish the feed throat. She now hold 5 rounds again, and smoothly feeds even big flat point cast bullets that used to hang up when seated all the way out to an OAL of 3.340" to fill the magazine. In big kicking rifles, I don't like much room for the bullets to slide around in the magazine under recoil and get all battered up.

Finding loading data is more challenging though. I did measure up and find the following fired case water volumes:
9.3x62 Hornady case, 76 grains
9.3x66 Sako case, 82 grains
9.3x74R Norma case, 81 grains

I noted that the Sako brass seems to be lighter constructed than the others as well, so to help extend its' life, I'll just use 74R level loads for general shooting and save the full loads for only serious hunting. I've loaded her up to 69 grains of both H4350 and Rx17 and a 286 grain Woodleigh before running out of room. I think H4350 might be too slow a powder and will try Varget.

These loads are compressed and need a good crimp to hold them when seated to 3.34", so I ordered a Lee factory crimp die. By the way, I told them to keep the dummy in case anyone else wanted to order one as well.

Anyway, I'm very happy with how this round about way of freshening up a bore turned out. I'll try and follow up later with a hunt report.

 

[ZG47]

Ok guys how about this the 12.7 x 108 necked down to 9.3mm. Might just fit in a long action magnum rifle .......

Back of a beermat calculations suggest that it would have a case capacity of 300 gr h2o ......would start to make the current 9.3 offerings seem a little weak and indeed underpowered .........Ohh well another one for the file .....

Accuracy life of 2-300 rounds?

 

[Clodo Ferreira]

Hi,

Looking at the difference of case volume between 9,3x62 vs. 9,3x66, about 6%, the velocity gain, loading both at roughly the same pressure, would be no more than 50 f/s. I am loading my ZKK 600 (60 cm barrel lenght) 9,3x62 at 2650 f/s with 250 grs bullets and R15 powder. Maximum entirely safe load at between 5 and 35 °C. So 2700 would be a realistic goal with the x66 one.

 

[Milehighshooter]

Clodo,

Yes, if loading to the same pressure there would be little difference. I factory, big difference as the x66 is just fast enough to satisfy countries with minimum FPE requirements in factory form. The x62 can be pushed, but factory loads and published data is stuck in the 1920's

 

[Clodo Ferreira]

Hi MileHS.,

Yes, indeed! The 9,3x62 factory loads are rather conservatives. Including the RWS loads that, usually are, for most cartridges, at the top pressure/velocity level!

 

[fsrmg1]

My internal ballitic program shows the 66 has a wopping 60 fps advantage over the 62 when both loaded to the same pressure, with identical bullets and powders.

This makes me think about the 74R, since it has equal case volume to the 66, in a strong actioned rifle like a Ruger No. 1, you should be able to easily match the 66 performance. Basically making it the equal of the old 375 Flanged Mag loading.

 

[Petrovič]

Hello and congratulations on your 9,3x66 (370 Sako) fsrmg1!!
I want to buy a new Sako in x66 or recut an older x62. It is much better choice for all round african cartridge! Even meets the NAmibia 5400 Jouls minimum for all Dangerous Game Hunting!! Most other countries will let it be used for DG, except few parts of SAR. This makes no point buying new x62, but x66. That extra 180 fts - 55 m/s (if u look at loading tables of Sako) is an important difference!
For ex. 286grs Hammerhead SP from x62 is at 710 m/s, while same bullet from x62 flies at 765 m/s! And 250grs TSX, in x66 flies easily over 800 m/s!
Now a question please. Where to get the best set of reloading equippment incl. Lee Factory Crimp Die, that u have ordered??? Any other tips for reloading?
Also where and for how much did u gate the recuttnig tools from x62 to x66.
Thanks.

 

[fsrmg1]

Ahoj Petrovic,

I just checked the Lee reloading website and they are still listing the 9.3x66 Sako factory crimp die under custom factory crimp dies ready to ship. Lee does ship outside the USA. After doing some full loads with Speer and Privi projectiles and seeing how the recoil battered the noses, a solid crimp is mandatory. For hunting I use use Woodleigh protected points and Barnes TSX. Both are up to the job and don't batter in the magazine. For powder, H4350 (AR2209) works good, but a bit slow and fills up the case before top loads reached. I found Reloader 17 great for it and really delivers the powder!

I use RCBS die set for 370 Sako Mag (9,3x66), it is great value and I am very happy with them. I was using the 9.3x62 die set seated out and they seemed to work good as well, they just didn't size further down to the base.

If you need a 9.3 Sako reamer, I can let you borrow mine. It has only cut one chamber and is to the Sako factory specifications. It totally cleaned up the 9.3x62 chamber on a Lothar Walther barrel.

Happy shooting to you!

 

[Petrovič]

Well, AHOJ!
You foud out I am central European. But I see u are Aussi, and I have even cousins in Perth, how interesting!
I want to thank u for your offer and for your long answer, very helpfull.
So far I do not own any of the kalibers, I was looking at used x62 in CZ (or simillar) and for a new x66 directly from Sako.
I like the lighter guns, so I may CHOOSE the Synthetic option (3,0 kg) or an ellegant Classic option (3,3 kg), because when u add todays heavy 1-6x24 (30mm tubes are standard) scopes, it is extra 1/2 kg plus rings, it comes to a 3.6 - 3.9 kg rifle! Want to use it as all rounder w. 250grs bullets, icluding DG with the 285-320 grs projectiles u mentioned.
Another option I was thinking was the O/U combination gun like the Haenel 9.3x74R/12-76 mag. (mainly because it is so lite -2.8kg) and easy to carry in a compact guncase. I just do not know if 2 shots are enough in a DG situation, as I am not very used to it (even buffalo with the heavy brenneke slugs have been killed by PHs, not to mention large predators). The drillings would be even better, but are quite expensive.
Cheers.

 

[ZG47]

Issue to consider with synthetic stocks, is that you often end up with a top-heavy rifle, due to stock being too light and poor fore-aft balance (for the same reason) Worth checking before you buy, as it is much harder to rebalance a synthetic stock with strategically placed lead or steel weights.

N.B. Top-heaviness gets worse when a scope is mounted.

 

[Petrovič]

Good point. What I usually do is to add a recoil pad, because I need extra 1-2 cm of stock length for my 190 cm. I have Kimber Montana synthetic (2.35 kg) in .308W and Browning Titanium in .325 WSM (2.8 kg) with extra 2cm r. pad u can just pull on, like a sock. It is not so ugly, if u put also a cartrige sock over it. They are only 22" and 23" long barrels, so they balance perfectly and the recoil is very manageable.

 

[fsrmg1]

My 9.3x66 is stocked in a classic Rigby configuration and I like the looks and balance of it. It is not overly heavy, but still has enouph weight to soak up some of the generous recoil.

I also have a nice Beretta Silver Sable II 9.3x74 o/u double rifle that has an extra set of 20 ga. barrels. This might be the way to go as well. That way you don't have to worry so much about huge point of impact differences between a 9.3 and 12 ga.

 

[Petrovič]

FAntastic. I Know Beretta Sable from katalog, as I baught the Ultra lite shotgun 12/70 years ago.
How long barrels u have, 56 or 61 cm? I was looking (today at hunt fair in St. Anton, Slovakia) at Verney-Carron SagittaireXS eXS in 9.3x74R O/U with 20/76 shotgun 71 cm exchange barrels. It is 56 cm and only 3.2 kg, all steel and slim round action. It should be around Eur 2800 extractor, and only E200 more for ejector, all incl. case (special price for east Europe I guess). Actually they gave me price, but they only had the ordinary Sagittaire Express One, which is not pretty.
DO u prefer ejector? I think it is definitelly worth it! Also no charge extra for double or single trigger (but then u can not choose the shooting barrel)!? The single trigger is faster and there is then no problem with the pistol grip being maybe too steep for larger hand like mine, when switching to back trigger.
How long stock do u need, because of shotgun? (On Beretta 12/70 I have 15 and 1/4", but on rifles only around 14 1/2" - 5/8" (in winter clothes), though I need maybe 14 3/4-7/8" in summer and on this V.-C. I would choose probably 15" (380 mm) pull if I could, shooting in Afrika in a T-shirt only. I also have baught nice leather recoil pad with rubber sleeve, that I can attach to the stock in seconds and lengthen it.
Also do u use on your O/U open sights, or Red dot no magnification or a small scope?
And finally did u use it on buffalo or elephant or would you?
cheers,
peter