Today I've got on of Gorilla Ammo's GF-10 rifles to do some shooting with. It's an AR-10 platform chambered for 8.6mm Blackout (they also offer it in .243 Win, .260 Rem, 6.5CM, and .308 Win). It weighs in at just 7.2 pounds with a 16" barrel, so it's not an NFA item (they do also offer a 12" pistol pattern). I've got my Q Porq Chop on it as a suppressor, and I'm using subsonic ammo - with this combination it is sort recoiling and completely hearing-safe. The loudest part of the gun is the action clacking closed after each shot. I only put about 40 rounds through it (thanks to the cost of 8.6 ammunition...) but I had no malfunctions of any kind, and it made a nice consistent ejection pattern.

We also took the opportunity today to put a round of Gorilla's 342gr subsonic expanding ammunition into a block of Clear Ballistics gel - and holy cow. It's a bullet designed to expand while retaining all its mass, and it sure does. The utility of the 1:3" rifling of the 8.6mm cartridge is that it provides a massive amount of rotational energy to allow the bullet to expand reliably even if it's traveling relatively slowly at range. It came out of the gel looking like an honest-to-goodness grappling hook...