Anyone know anything about 370Sako aka 9.3x66

[Shawnba67]

I was certain I was gonna put together a 9.3x62 on a win 70. Then I read about the 9.3x66. Cost wise it seems like it will cost $80 more to get going on the 370 over the x62. What kind of fps gains would I see running both at 62k pressure? Ideas and opinions welcome. Thanks Shawn

 

[JBT47]

https://www.americanrifleman.org/Webcontent/pdf/2009-11/2009111213938-federalsako.pdf

 

[Kurz]

What kind of fps gains would I see running both at 62k pressure?

Virtually, none. There is approximately 3 grains of capacity difference between the two cartridge cases, so you do chronograph a few FPS difference but certainly nothing noticeable for game. The x66 case is longer and contains more capacity but the bullet gets seated slightly deeper because of that case length with regard to the magazine length. The x62 case, being shorter, actually has a little bit more usable case capacity when the bullet is seated at magazine length but again the difference is inconsequential.

I shot three different cartridges at one point to determine which one I wanted. This included the 9.3x64 Brenneke, which is a bigger case in diameter as well as the 64mm length. It has roughly 7-8 grains more capacity than the 9.3x66 Sako. In the end, the 9.3x64 Brenneke was my choice because of the increase in velocity which yielded more energy at the target, which was my goal. I could get about 125-150 FPS from the Brenneke when compared to the other two cartridges, getting me about 600 ft/lbs of energy.

All of my testing was done with the same two bullets, the 286 grain Nosler Partition and the 286 grain Barnes TTSX and about 6 different powders. The barrels were all 25.6" (650mm) for the tradition barrel length.

The biggest difference I noted throughout the tests was the lack of quality (consistency) of the Federal brass. This was also instrumental in my decision since the 9.3x64 Brenneke is available in RWS brass, noted as being the best in the world. Yes, you can argue this statement but it is apparently held up by tests. The RWS brass is also significantly more expensive than domestic brass, but still, it's the lasting quality which wins the day for me.

Regards.

 

[jbhotrod]

I always thought the x64 Brenneke would make a great base for wildcats...kinda like a -06 length .284 case from what I remember, without checking and confirming dimension.

 

[BCBRAD]

I have one in a Sako M-85. It will run 250gr bullets ~ 2660-2700 ft/s and 286's at 2525 ft/s. Ramshot Big Game is the go to powder. Accuracy is ~1moa for 5 shots.

I use Sako head stamped brass which I think is made by Norma.

If I did it again I'd go with the '62, for the brass and getting bullets with canna lures to line up with factory COL.

 

[SeabeeKen]

What I did was build a 9.3x62 and run 370 sako brass into my 9.3x62 die and trim to 62mm. This allows me to run my x62 at 370 pressures. Significant difference. I run 250 gr at 370 sako speeds