Introduction

Every so often there are new cartridges that break onto the shooting scene, most of the time it is part of a marketing campaign, but sometimes there is a higher purpose. Some new cartridges offer a marginally better performance like some extra feet per second, or a faster twist for modern bullets. But today we are looking at a bit of an oddball, in that to some folks it seems like a step in the wrong direction. The subject of discussion today is the very popular fast twist and quiet shooting: The 8.6 Blackout. A relatively new cartridge brought to us by the folks at Q LLC.

Blackout Background

The bigger blackout, the 8.6 follows the same line of thinking as the popular 300 Blackout. *Record scratch* The 300 Blk has been around for a long time, first as the 300 Whisper. The cartridge has done well particularly in AR15 platform rifles. Its main idea is contrary to popular trends in ammunition; slowing bullets down to reduce the sound signature. Of course with slower velocities the only way to keep energy on target up is to increase the bullet weights used in these situations. The heavier bullets typically shot at these slow speeds, require faster than average twist.

Slowing bullets down to below the speed of sound is by design with Blackouts, doing so removes the supersonic shockwave produced. And when coupled with a suppressor to remove the muzzle report of the firearm, the result is near movie quiet shooting. This is where both Blackouts shine, when they are shot suppressed with subsonic bullets, there is a level of anonymity that is appealing to many hunters.

The 8.6 Blackout

It should come as no surprise that the boys at Q came up with the 8.6, carrying on from their previous work. The cartridge is based off of the 6.5 Creedmoor case, that is opened up to accept .338 caliber bullets. Bullets typically weigh between 200 and 350 grains, again, using heavier bullets is part of increasing energy on target when increasing velocity is not an option.

Loading the 8.6 Blackout is usually done with faster burning powders typically used in pistols and cowboy cartridges. Again, this is because velocity is not the goal of the 8.6. It has a very specific purpose, to propel big bullets right up to the speed of sound but not exceed it.

I was turned onto the 8.6 Blk a few years ago, when I sat down to speak with Ian McCollum of Forgotten Weapons. As nerds often do, our discussion quickly went to numbers and the science behind 8.6 ballistics. A brilliant part of the 8.6 design that departs from the 300 Blk predecessor, is the barrel twist. Taking the fast twist for heavy bullets to an extreme, has more than just stabilization benefits. The 8.6 typically uses a one twist in three inches (1:3), yes it almost looks more like threads than rifling. This incredibly tight twist does far more than stabilize long and heavy bullets.

The Numbers

Let us again look at numbers, the point of the Blackouts is to keep bullets under the speed of sound. Subsonic bullets are quiet, and if you can’t increase speed the only way to increase the energy on target is to increase the mass of the bullet. At least it was the only way, but there is another. The 1:3 twist of the 8.6 drastically increases the rotation of the bullets, and as the RPM of 8.6 bullets increase, so does the energy they impart on the target.

This of course only works if the bullet grossly deforms from its smooth shape. Imagine if you could, removing the blade of your favorite blender, and putting a bullet in its place. Even if you filled the blender with tomatoes, the spinning bullet wouldn’t do much. But imagine now that the bullet opens up like some are designed to do, with broad petals and increased diameter. You can imagine what this blender bullet might do to organs, even though its velocity is subsonic.

Popular Firearms in 8.6 Blackout

As the popularity of the 8.6 has increased, many firearm manufacturers have brought new guns to the market chambered thusly. And the volume of manufacturers doing so, seems to show some faith in the concept. It would be far too time consuming to list them all, but its safe to assume you can find one from your preferred brand. Whether it be one of the Fix’s by Q, or one of the CMMG variants, or more bargain branded guns like Bear Creek Arsenal. The 8.6 I am shooting today is like many others a custom one, a sixteen-inch 1:3 twist barrel for my Desert Tech SRS.

Of course the 8.6 Blackout can also be used as a supersonic cartridge as well. There are plenty of options out there in the 180-230 grain class that can also be used. Though my personal opinion is if you are going to shoot super sonic cartridges there are better options.

Suppressors

Shooting the 8.6Blk without a suppressor makes no sense to me, so I wanted to try a few different options to see what worked best. It should come as no surprise that the CGS Group Hekate won that competition. This DMLS suppressor is well known for its superior suppression, and it made the 8.6 sound like a distant duck fart in quiet water.

I purchased a set of dies by Lee Precision, and started trying various loads to see where the 8.6 would take me. I will say that I did find it a touch more challenging than loading the 300Blk. It took a little more work to find the right powder and suppressor combination that would produce quiet results.

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Comparing Subsonic Bullets to SuperSonic
Velocity	300gr SMK 8.6Blk	% of Loss from start	300gr SMK 338LM	% of Loss from start
Muzzle	1000 fps / 666 Ft lbs	100%	2730 fps / 4963 Ft lbs	100%
250 Yards	965 fps / 620 Ft lbs	96% fps / 93% Ft lbs	2484 fps / 4111 Ft lbs	91% fps / 83% Ft lbs
500 Yards	932 fps / 578 Ft lbs	93% fps / 87% Ft lbs	2250 fps / 3373 Ft lbs	82% fps / 68% Ft lbs
750 Yards	900 fps / 539 Ft lbs	90% fps / 81% Ft lbs	2027 fps / 2738 Ft lbs	74% fps / 55% Ft lbs

Want to read about another big subsonic cartridge? Click here