I figure Kase has researched the topic maybe GNR
I first thought the "new" 8.6 Blackout was a gimmick. It is actually a .338 on what amounts to a shortened and modded .308 (6.5 Creedmore or .30 TC) case. The thing about this new round is exceptional performance in a suppressed form. That is below 1100 fps. Getting something to more than simply poking a hole at that speed is what many people are after. Tumbling slugs, pre-fragmented, hydraulic displacing, specialty slugs have been the innovative trends. They all have showed some success. Plus the supersonic performance is not bad either in the 2200-2400 fps range. Nothing to sneeze at.
This 8.6 requires a .308 size platform. For a semi that's AR10. The true innovative and striking feature of this round is it's rate of twist! THAT is what has made it so innovative and high performing. It specs a CRAZY 1:3" twist rate. I think I read the spin on the projectile is on the order of 500,000 RPM! Normal bullets simply turn to powder exiting the bore or jump the rifling in the bore. It specifies specific solid alloy projectiles or special heavy jacket bonded bullets, even at sub-sonic speeds.
That's long story short a one turn in three inches of bore rotation. It's crazy and unconventional but there is something to the physics. I find the fresh approach interesting for the future.
I looked at the 8.6 when it came out,
but went with the 375 Stalker instead. The 375 flopped and the 8.6 prospered.
The 375 Stalker is the same 308 case cut to 1.560" and necked to .375". I built mine on the AR15 platform as it uses a 7.62 x 39 bolt and standard AR15 magazines loaded single stack. I run 270 grain cast powder coated bullets @ 1060 fps with a suppressor. I can run 220 grain Hornady's up to 2200 fps.
![[image]](https://i.imgur.com/8aZNEdDl.jpg)
I built mine in 2021 and haven't really done much with it. I need to get it back out 
I wonder if a cast bullet could take 1:3 rifling?!
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I'm not sure.
My 375 Stalker is 1-8" and it shoots fine. I don't understand the need for 1-3"
That’s the secret it seems, Uber high rpm
It creates impressive energy transfer even going slow fps. It makes me curious, it’s different for sure. I bet there is some way to make it work, but that 1:3” is hugely different than anything before.
Some type of hard cast with coating perhaps. Even the expanded bullets are marked by the radical rifling marks.
A fast twist uses up a lot of energy.
Imparting spin to the projectile creates drag.
And 1 turn in 3" isn't "fast" .. it's RAPID!
Lots of interesting testing being done.
This clip I took a peak at is the exact same ammo, gun, speed, material. The BOTTOM block was just the 1:3" twist rate barrel. You can see the different spiral pattern and noted more energy transfer due to the crazy spinning.
![[image]](images/uploaded/202404192004286622ce4c740da.jpg)