Anybody running a KX3 on their SBR??

Using the KX-3 on an SBR, with even a 7.5" barrel, one can be surprisingly safe from blast ... IF ... one is behind the muzzle's three-nine line. In front, even a little bit, is pretty amazing. At short range, it will blow a nice big hole in cardboard targets.

As far as flash is concerned, the KX-3 is a flash enhancer, not a flash suppressor. Even decent quality ammo like M855 creates a basketball size fireball in front of the gun. Sometimes, those targets as mentioned above with the holes blown in them are set afire!

Other drawbacks of the KX-3 are weight, length, and expense.

For a V-SBR ("VERY" short barrel rifle - under 10.5") or AR' pistol upper, I've found that the Troy Claymore is lighter, shorter, cheaper, and a better flash suppressor, all with no accuracy degradation. Here's a shot of the Toy Claymore on a Noveske 8.2" .300 BLK barrel:

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When I removed the KX3 from a 12.5 noveske upper in order to install a suppressor mount, I fired the rifle a few times without the muzzle device. I was a bit surprised to realize how effective the Kx3 was at reducing concussion and felt recoil. It's not a genuine brake, by any means, but it IS effective.