How does it perform?
I picked up an 8.6 barrel made by Ballistic Advantage, which has 5/8 x 24 threading. Playing the long game with this build as this is a "new" cartridge. I wouldn't doubt the further above posted criticisms are/were warranted at the time.
What seems important to know about 8.6 Blackout in mid-2024 is...
It remains a niche cartridge with its main usefulness being <300m big/dangerous game hunting and the fact that it'll run in SAs/AR10 platforms.
The 1:3 twist only works with bonded or solid copper bullets, and based on ballistics gel tests the rotational velocity is not a sales gimmick.
The industry is moving towards acceptance, hence barrels/complete uppers being made by more companies (QA still needed however).
Gorilla, Fort Scott, Aitken Arms, and Western are manufacturing ammo, with factory new brass.
There doesn't seem to be much point in getting into this cartridge without a silencer and a short barrel, so pony up for the ATF.
The ballistics gel is the selling gimmick.
So is the whole 3 twist...a total gimmick.
I bought into it as soon as it came out, figuring it was a gimmick...it is and totally unnecessary to stabilize the bullet, and adding nothing to killing power, but maybe 20 ft/lbs of rotational energy, while losing that same amount in foreard velocity energy...with the same powder charge... physics.
I went to the 6.5 twist and a whole new world of high velocity and subsonic accuracy became available....with no worries of bullet blow ups of any bullet lead or copper.
The 3 twist AR has been scrapped, and replaced with a 6.5 twist bolt gun.
Now I can run 350 gr Maker subsonic to almost 1700 fps with no bullet blow-ups or getting the velocity just right.
Any cheap lead bullet as fast as the 8.6 can shoot them...right up to 338 Federal levels.
So why put up with the limitations of a 3 twist, when a 6.5 twist will stablize a 350 gr Maker at 750 fps, at -20°, at sea level, and still have plenty of room to spare, for bullet stability.
2800 fps with Barnes 160 gr.
200 gr Speer 2573 fps
Over 2400 fps with 225 gr lead excellent accuracy.
Almost 2000 fps with 300 gr SMK
No bullet blow ups plus good accuracy with both subs and supers.
My advice after owning both is, scrap the 3 twist, and go to the 6.5 twist...it solves all the 8.6 problems.
No down sides, and pick up a bunch more super killing power, cheaply, if desired.
Plus run the cheap lead bullets as slow or as fast as one wants.
The 200 gr Speer at 2573 fps is cheap fun accurate and deadly...but can be run at 1000 fps or anywhere in between for cheap fun shooting, with no worries.