450 bushmaster Archives

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

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