Tag Archives: subsonic

Fast Twist and Quiet Shooting: The 8.6 Blackout

May 22, 2025blog300 blackout, 300blk, 338, 338 arc, 338arc, 450 bushmaster, 450bm, 8.6 Blackout, 8.6 BLK, 8.6blk, subsonic, Suppressedcoldboremiracle

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.

athlon Rangecraft velocity pro chronograph, Garmin Xero C1 chronograph, chronograph, comparison, review, garmin, athlon, 8.6 blackout, — the Athlon Rangecraft Velocity Pro Chronograph was used to measure velocity

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.

the **CGS Group Hekate 338 suppressor** was a fantastic option to keep the 8.6 quiet

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.

8.6 Blackout, 8.6blk, brass, loading, desert tech, srs, srs a1, sig sauer, tango 6

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.

8.6 Blackout, 8.6blk, brass, loading, 300 grain, sierra match King — The 300 gr. Sierra Match King is a great bullet for the 8.6Blk, they were provided by **Wideners Reloading supplies**

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.

8.6 Blackout, 8.6blk, brass, loading, desert tech, srs, srs a1, sig sauer, tango 6, anechoic, anechox 35, suppressor

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.

my **Desert Tech SRS 8.6Blk** with the **Anechoic Anechox 35 suppressor** and **Sig Sauer Tango 6 riflescope**

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.

a little spread of some of my **8.6 Blk handloading supplies**

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.

Continue Reading Here

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

Left to Right: 300 Blk, 8.6 Blk, 450 Bushmaster, 338 Lapua Magnum. The three on the left are loaded subsonic for quiet work

Want to read about another big subsonic cartridge? Click here

Are Subsonic Cartridges Superior?

March 16, 2025blog300blk, 308 win, 338arc, 8.6blk, silencer, subsonic, supersonic, suppressor, velocitycoldboremiracle

Introduction

More and more often, we are seeing interesting developments when it comes to bullets and ammunition. Today I wanted to discuss an interesting situation regarding velocity of bullets, and how specialty designed slower cartridges are changing the future of shooting. Are subsonic cartridges superior? Well, depending on your purpose they just might be.

The velocity of a bullet when fired from a firearm has a lot to do with its utility and purpose. Most rifle bullets travel at supersonic speeds, that means they travel faster than the speed of sound. Conversely, many handgun bullets travel near or below the speed of sound. For the most part, this has been a result of typical construction limitations for both firearm and ammunition manufacturing. Handguns typically have less room for large powder capacity cartridges, which is why they are typically slower. Which is also why rifles often have much higher velocities, as rifle cartridges often have more room. Additionally, rifles need greater range than most pistol cartridges, which has resulted in their design for more velocity.

typical pistol cartridges (left) with a couple rifle cartridges (right). Even though all these cartridges have similar bullet weights, the velocities are around double from rifle rounds.

What is the Speed of Sound?

The speed of sound is determined by how fast a sound wave travels through air. We have all witnessed curious situations where we see something far off before we hear the sound. That is because the sound takes much longer to get to us than the light reflecting the image to our eyes.

To add another layer of complexity, not all air is the same. The speed of sound is relevant to the current atmosphere the sound is traveling through. Humidity and air pressure can greatly effect air density and therefore the speed of sound will change depending on the atmospheric conditions. For example; warm dry air will result in a higher speed of sound than cold humid air.

Moist air has visible effects as well as invisible effects

Why does this matter? Because bullets also travel through air, and they are also equally effected by atmospheric conditions. As a bullet travels through the air it encounters resistance, and much like a boat traveling through water, once it starts moving fast enough it creates a wave. The pressure wave caused by bullets traveling faster than the speed of sound creates a sonic boom. This is why even when using a suppressor, most rifles are still quite noisy. Because the bullet itself is breaking the sound barrier which is quite loud. The suppressor removes most of the noise caused by the report of the rifle, but the supersonic bullet causes its own noise.

This image shows both the sound waves caused by the bullet, as well as the waves coming from the unsuppressed muzzle

Subsonic bullets, those that travel below the speed of sound do not create the pressure wave or sonic boom. Much like a boat that idles across a lake doesn’t make much of a wave. And if you use a suppressor to remove the report of the firearm, these bullets can be fired pretty quietly. Almost like you see in the movies, just less stupidly.

Why would you want Subsonic vs. Supersonic?

Subsonic shooting with a suppressor can be very fun, and extremely useful if you are a hunter. Shooting a whole pack of coyotes could be doable with marksmanship and such silent shooting. The appeal of this covert shooting ability has enticed many shooters and engineers alike. Which has resulted in various new firearms and ammunition lines that are specifically designed for this purpose. Cartridges like the .300 Blackout and 8.6 Blackout have received a great deal of attention lately as suppressor use has skyrocketed. The use of these cartridges with a suppressor has made super silent shooting a reality, and it has become very addicting to those who practice it.

Culling some pest turkeys in suburbia is better done suppressed and subsonic, this was done with the **TX22** and a **Silencerco suppressor**

It is important to understand the limitations of these specially designed products. There are ammunition lines and even cartridges that are specifically designed for subsonic use. Purpose built subsonic cartridges and bullets tend to have more limitations because of velocity. In order to maintain their speed below the speed of sound there are few ways to add energy other than increasing the size of the bullet. Some folks like those at Discreet Ballistics have designed solid copper expanding bullets, to increase the transfer of energy on impact. Another theory though disputed by some; is that increasing the rotational speed of the bullet can add energy on target. This is achieved by using fast twist barrels like one-in-five, one-in-three or even as fast as one-in-one twist barrels.

The lower velocity of these bullets can greatly alter the effectiveness of them at extended distances. While it can be done, subsonic cartridges are much more susceptible to variations. And those variations are more pronounced as you cover more distance. The anonymity of super quiet shooting can be very valuable, but requires an extra level of understanding to know when and where it can be applied effectively.

This buck fell to a single shot from a subsonic 450 Bushmaster, a **405 grain solid lead-cast bullet** with a flat meplat. The sound of the bullet impacting the deer was much louder than the gun going off. My **Desert Tech MDRX**

Standard Cartridges Too

Standard cartridges can also be down-loaded to subsonic speeds, particularly those that aren’t that fast to begin with. I used to load my 308 down with subsonic 220 grain bullets, and they were fun, and quite useful.

My **Desert Tech SRS** A1 Covert with a 16″ 1:3 twist 8.6 Blackout barrel and **Anechoic suppressor**

I’ve also loaded my 450 Bushmaster down to subsonic speeds and increased the bullet weight significantly for added performance. There is an added benefit to this scenario, a 308 can shoot subsonic bullets much like a 300Blk, but it can shoot much better when loaded with supersonic ammunition. A subsonic 220 grain bullet fired from a 308 chamber vs. a 300Blk chamber will fly the same all else being equal. But say you want to increase your energy on target and distance by changing bullets and powders for supersonic use. A 165 grain bullet fired at supersonic speeds from a 300Blk will be nowhere near as fast as one fired from a 308 chamber, all else being equal.

Its easy to see why the 308 Winchester (top) can achieve much higher velocity than the 300Blk (bottom) when both are shooting supersonic 150 grain bullets

What Not to Do

Many manufacturers have jumped into making firearms chambered for some of these dedicated subsonic cartridges. And that has resulted in a great deal of adoption by folks from every walk of life. It should come as no surprise that some are shooting dedicated subsonic cartridges and ammunition through firearms without a suppressor. While they are perfectly happy doing it, they certainly aren’t getting the bang for their buck. Shooting unsuppressed with subsonic cartridges like the .338 ARC or .300BLK is like wearing flip-flops to go hiking. The greatest asset of these cartridges is shooting silently with a suppressor, so if you aren’t going to use a suppressor, why cut your velocity, energy and range for no gain? Perhaps you might have another reason, but anything you can do with a subsonic .300Blk can be done better and for less with something like a 5.56 or 6ARC. The best advantage of the Blackout is its silent shooting, so if you’re going to shoot loud, you may as well shoot something better.

This fox was far too brave, walking between us in camp in the dark. A subsonic 308 quietly put him out. And later that day, the same rifle (different ammo) was used to shoot a cow elk 200 yards away.

The Right Application

As you might have gathered by now, there is a perfect application for subsonic shooting. A scenario where you need exceptionally quiet shooting, whether that be dispatching pests or something else. For example; a subsonic 22lr is great for taking out rats covertly in the dark. And if you use the slightest bit of imagination you’ll come up with other ideas. It is these specific scenarios where a subsonic cartridge is superior to supersonic options.

Suppressed subsonic 22 pistols are very handy for dispatching pests, this one is another **Taurus TX22** with a **YHM Phantom** suppressor

450 Bushmaster, Slow and Steady Wins the Race

February 9, 2020hunting, Shooting hardware450, 450 bushmaster, 458, subsonic, Whispercoldboremiracle

Introduction to the Bushmaster

If I had a rifle for every time I fell in love with an idea, the world would lay quietly in a torpid slumber beneath a blanket of heaped weapons strewn beyond the horizon. I was blessed with a vivid imagination since childhood. My mind is in a perpetual cycle of finding project ideas, digesting them mentally until my brain has either built the whole thing and tested its flaws or until the same has been exhausted to the smoldering dumpster where ideas die. If it weren’t for the occasional successful brainstorm that ends with a nifty new project, I might lose my mind. This is a story about one of those.

450 Bushmaster cartridges loaded with Hornady 350 grain round nose bullets, these bullets were .458 until I swedged them down to .452 for the Bushmaster

The 450 Bushmaster

I have long wished for a slow and heavy cartridge that could readily be used for subsonic launching of big, heavy bullets that will go a very long distance. There were many possible suspects; big bore cartridges, the Whisper family, and many others. I had long wished for a 510 Whisper, but my suppressor inventory ventured only to the .46 mark. Making the 510 and similar cartridges inapplicable. The next best thing for a diet of heavy and slow would then be something in the .45 realm.
But even then, .451 or .458? Why not both?

The .458 bore has a much larger and heavier selection of bullets, and they are easily swaged down to .451. Which makes a perfect fit for the 450 Bushmaster. The 450 enjoys quality brass from Hornady and Starline, making reloading a snap. And using mild charges for subsonic velocities would keep the brass life high. The straight walls of the cartridge would hopefully last to be reloaded again and again.
The beauty of my main rifle, the Desert Tech SRS A1 Covert, is its multi-caliber role. I have a pile of barrels accumulating for it in my safe, so starting this 450 project was as simple as a barrel, some dies, and some powder and bullets.
The sixteen and a half-inch barrel was made by ES Tactical, crowned and threaded for my SilencerCo Hybrid. It didn’t take long to start falling in love with this basically large pistol.
I found that the factory Hornady Black 450 Bushmaster ammunition was a good place to start. At 100 yards it was printing groups just under two inches, I was hoping for better so I tried my hand at reloading. A set of dies for the BM isn’t as easy to come by as other calibers, all I could find were Hornady and another set from Lee Precision. I opted for the Lee set, which I still don’t regret. The four die set has allowed me to load quite a bit of very precise ammunition.

Seeing as how my objective was to eventually reach a heavy subsonic load, I went ahead and ordered Lee’s .458 to .451 swage die. That way I could take advantage of the larger and heavier selection of bullets in the 458 family. I wasted no time in doing so, some of the first reloads I tried were Hornady 350 grain round nose bullets swaged down to 451. They did pretty well, but I wanted bigger, so I purchased a box of 405-grain lead bullets that had been made for the 45-70. The lead slipped easily through my swage die, and in no time they were 451’s.

Subsonic loads for the Bushmaster used 405-grain lead solids, these were made to shoot in the 45-70, but after running them through the Lee sizing die, they ran perfectly through my Bushmaster

I tried a couple different powders, but as usual, when it comes to subsonic shooting, IMR Trailboss powder was the ticket I needed. I was blown away with the consistency of the results, I was seeing velocities more consistent than anything I had loaded prior. Not only single digits but SD numbers in the 1-4 fps range. I was praying that this would translate into extremely accurate ammunition, it wasn’t bad but not as good as I’d hoped. Accuracy still averaged around 1-1.5 MOA at 100 yards, good enough to hit most targets of mine at the ranges we expected.

My excitement about this whole Bushmaster project was tripled when Mad Scientist/Gunsmith Eric Smith built me a second barrel, this time for my Desert Tech MDRX. The MDR is a semi-automatic bullpup, it brings accuracy and multi-caliber universality to a compact and quality package. I couldn’t wait to try my same loads in the MDR, I figured it likely wouldn’t cycle the action but I wanted to try anyway.

The accuracy was almost the same from the MDR as from my SRS A1, but as I feared it would only cycle the faster supersonic ammunition. I am currently working on an alteration to make it cycle, if it works out, it may be the coolest thing ever.

Hunting with the subsonic 450 Bushmaster

The goal, of course, was to use this project for some very quiet hunting. Sneaking into bow range of animals is exciting enough, but the ability for movie quiet rifle shots with one MOA accuracy made it even more exciting.

This past season we were able to put it into use, and the results were exactly as I had hoped. We had eyes on a small group of mule deer that we could predict movements with some regularity, so a good hide was fashioned that would give a view of them with no more than 120 or so yards max range. As it turns out, a young buck made his way across the opening one dusky evening, and he wandered around the 60-yard line.
The hushed report of the Bushmaster made every ear in the group perk up, but only one of them jumped. He jumped from the impact of the bullet, which hit him right above his right elbow, and passed through him exiting almost exactly opposite. He ran for about 20 yards where he toppled over and kicked on the ground for a short time.

This young buck hoped to escape from the **Desert Tech MDRX 450 Bushmaster**, but a perfect shot through both lungs shortened his run to a 20-yard dash before he toppled

Internal inspection of the buck showed perfect damage to his lungs, the bullet passed through both lungs rupturing many vital passages along the way. His lungs quickly filled with blood, causing what most of us would call a near-perfect kill. Another positive result was very minimal meat damage, the lower velocity didn’t seem to cause all the bloody mess that supersonic bullets tend to do. It was more reminiscent of an arrow wound.

Final thoughts

With experiences like this and all the other advantages that it brings, this will likely not be the last time we use the 450 Bushmaster for a hunt. While the purpose I have described here today may not be orthodox, it shows you what can be done with a little imagination and firepower.

-CBM