This write up began life as a comparison between 338 Spectre, 338 ARC and 8.6 Blackout. However, as I began to dig into the comparisons, it quickly became clear that we needed to spend more time on the 8.6 Blackout and that was in a class of cartridge on its own. While we can draw comparisons to both the 338 Spectre and the 338 ARC, the bold claims made about 8.6 Blackout and the supporting data really tell an interesting story on its own.
338 caliber is sometimes known as 33 or 8.6mm, has been a somewhat niche cartridge; it tends to find markets in medium to large game hunting. 338 Federal, 338-06, 338 Win Mag, 338 RUM and most recently the 33 Nosler are examples of this. When ELR started becoming popular the 338 Lapua Magnum was popular for about a second as it was more affordable than the 50 BMG. That moment passed and we saw the market moved on to 338 Norma, 33XC and 338 Edge. At this point I think most of the serious ELR guys have moved on to larger 375, 408 and 416 calibers.
Even when 338 cal was popular no one got as excited with new 338 cartridge as they do with, say a new 6mm chambering. This is probably why when 8.6 Blackout was introduced at the 2022 SHOTShow, its subsequent fanfare caught many people by surprise. A few years later the 338 ARC again has grabbed the attention of many, mainly thanks to the marketing powerhouse that is Hornady.
I have been watching the 8.6 Blackout ever since I was introduced to it at the 2022 SHOTShow. I was deep into getting my 338 Spectre figured out and this immediately caught my attention. However, it just was not in the budget for me to invest in a new rifle and so I have been watching on the sidelines. Ever since I started making jacketed bullets for my 338 Lapua, I have been on the lookout for more cartridges that I could use my Corbin Dies to make bullets for. Once you have made that investment, you try and stretch it as far as it can go.
A Quick Backstory
To understand the 8.6 Blackout, we must look at its little brother, the 300 Blackout. The concept of the 300 Blackout was not new, J. D. Jones at SSK Industries introduced the 300 Whisper in the 1990’s which is so close dimensionally that you might think they are interchangeable (they are not). The story of the 300 Blackout is more of the right idea at the right time marketed by the right people. I am a fan of the cartridge as it is versatile. You can shoot 220 cast bullets which have all the energy of a 45 ACP but in an AR platform, then you can switch to a 110 grain Barnes TTSX and have a potent whitetail cartridge, or something great for home defense.
In fact, the 300 Blackout was adopted by and used by SOCOM for several years. Barnes had the ammo contract during my tenure there. They were loaded with a special brown radiopaque tip which would show up on X-rays, to aid field hospitals and surgeons who had to treat the bad guys who survived. Due to its popularity, 300 Blackout was accepted as a SAAMI cartridge and remains a popular chamber for ARs, though I think it’s starting to wane.
The 8.6 Blackout was built on the same premise, by the same folks that brought us the 300 Blackout. Kevin Brittingham, once the founder of Advance Armament Corp (AAC) and then subsequently Q, decided to add a twist (literally) to the design. They took a 6.5 Creedmoor case, shortened it slightly, and necked it up to accept a 338 (8.6mm) bullet. Typically to stabilize a subsonic 300 grain bullet you need a twist rate of around 1:8 and if you want to go a little heavier, a twist rate of 6 is not unwarranted. However, Q decided to add a twist rate of 1in3 which was a bold design decision.
The marketing buzz centered on the ‘Blender Effect’; the idea that increased rotational speed enhances terminal performance. This was backed up by some very convincing Ballistic Gel Tests. It is built on a sound premise, the faster the twist the faster the bullet is going to spin, and just how fast is the spin?
It Spins How fast?
To give you an idea of how much rotational speed you got from going 1:8 twist which the 338 ARC specs to a 1:3 twist that the 8.6 Blackout boasts I put together a chart.
Rotational speed is determined by two things, the twist rate of the barrel, and the velocity of the bullet when it leaves that barrel. For subsonic the velocity is conveniently capped, typically manufacturers shoot for 1050fps to keep the round safely below the speed of sound, regardless of if it is shot at sea level or in the Rockies. Rotational speed is not linked to the bullet weight; it does not matter if it is 160 grain bullet or a 350-grain bullet. If it leaves the barrel a 1050fps from a 1:8 twist it will be spinning 94,500 RPM.
As we can see, the 1:3 twist produces nearly twice the RPM as a 1in6.5 barrel. Immediately the results look impressive. The number is so large in fact that I think most people would have a hard time comprehending how fast that is. To give you a little perspective your engine idles around 800 to 1200 rpm, and when you’re cruising down the highway around 2000-2500 feels comfortable. Prior to the 2014 rule changes, Formula 1 engines had rev limiters set around 20,000 rpm. Jet engines routinely turn around 30,000rpm.
In fact, the only thing most of us ever see spinning anywhere near the RPMs of 8.6 Blackout shows up in your mouth. Dental drills run around 250,000 RPM or more. If you’ve ever listened to one, you can hear the pitch sag the moment the dentist puts even the slightest pressure on it. That drop in pitch corresponds to a loss of tens of thousands of RPM. Despite the insane speed, the torque is basically nonexistent. The little turbine is running on air pressure, so it’s not exactly a powerhouse.
A bullet has a similar property as a dental drill. It leaves the muzzle at a high rate of speed, but the amount of energy that is required to spin up the bullet is actually very little, and it’s also pretty easy to calculate. The energy at play here is referred to as Rotational Kinetic Energy, which is a mouthful so we’ll call it rotational energy. We only need to know the mass of the bullet, the diameter and the rate of spin. To keep things simple, I compared the rotational energy for the 338 Spectre, 338 ARC and 8.6 Blackout, all using a 300 grain Sierra MatchKing. (For added comparison I also added the same 69gr 223 Remington load as we had before.)
Again, the graph shows that there is a notable increase in the energy content of the 8.6 Blackout over its peers. It is also worth noting that the 223 Rem load came in far lower despite having both a higher muzzle velocity, and a higher spin speed. This belays the fact that a smaller bullet takes less energy to spin to higher RPMs.
Without context the 45.7ftlbs looks to be substantially more than the 338 Spectre, again it would seem that there is truth to the coined “Blender Effect”. The energy must be there to be transferred. However, these numbers also lack context, how much energy is 35ish foot pounds?
When we calculate energy muzzle, we only consider the linear energy, and we do not calculate the rotational energy. The chart below clearly demonstrates why the amount of energy it takes could be considered a rounding error. With the 8.6 Blackout even with its increase 1in3 twist the rotational energy of the bullet amounts to roughly 4% of the total muzzle energy.
To put it in a different way 35ftlbs is roughly 1/3 the muzzle energy of a 40gr 22LR with a muzzle velocity of 1200fps. Another way to look at this, the energy of a typical 9x19mm load is between 320 to 350 ftlbs, a 45 ACP (The Lords Caliber) develops somewhere between 380 and 400ftlbs. The difference between the 9×19 and the 45 ACP has been one of the most hotly debated topics until recently when the market opinion has decidedly moved towards the godless 9x19mm (Obvious progression towards the end times). The difference in energy delivered? 30 to 40 ftlbs.
Terminal Performance
Terminal ballistics is a difficult subject. To study it properly, something has to die. Yes we can shoot ballistics gel and take measurements and largely we can make statements such as, “The bullet dumped most of it’s energy in the first 12 inches of penetration as evident by the temporary and permanent wound cavity. Ultimately the bullet penetrated 18in, expanded 1.5 times it’s diameter and kept 95% of it’s original mass”. What is much harder is comparing two bullets of similar make and performance and say with any level of certainty that “Bullet A” will result in a more ethical kill, or a faster kill, then “Bullet B”.
That’s really what this comes down to. On paper, you can argue that 8.6 Blackout carries more energy thanks to the added rotational component, but translating that into measurable terminal performance is a different story. There are too many variables that ballistic gel simply can’t simulate, like the changing density of tissues and bone. There might also be another factor at play. Most of the premium 8.6 Blackout loads use machined copper bullets in the 350–360 grain range.
One of the challenges with subsonic ammunition is getting reliable expansion. There usually isn’t enough energy to make a bullet mushroom, even with a soft lead core, because the exposed meplat on a spire-point bullet is relatively small (less of an issue with blunt pistol bullets). Getting copper to mushroom reliably and consistently is even tougher. Lead deforms mechanically; copper usually relies on hydraulic pressure. It’s entirely plausible that a higher rate of spin could help initiate expansion in a copper bullet. That said, I haven’t found anything that proves or disproves it, so it may just be my own conjecture.
That is where a machine copper bullet comes into play. Unlike the Barnes TSX, or Hornady’s GMX bullets, which are swaged. A machined copper bullet is precision machined on a Swiss Lathe, and can achieve impressive expansion and perfomance that is just not possible with a conventionally swaged copper bullet. Unfortunately this comes at a price, these machined bullets are sometimes 2-3 times the cost.
The ultra fast twist rate of the 8.6 Blackout often means that traditional cup and core lead bullets are not going to work. In order to get the bullets to expand, the jackets have to be thin, but thin jackets do not hold up to the ultra fast twist rates of the 8.6 Blackout. They will litterally explode from the centrifigal forces.
The Price of Speed
This additional energy that is gained from an ultra fast twist rate does not come without a price. It severely limits the performance of the 8.6 Blackout when it comes to supersonic loads. A natural bullet selection for a supersonic load in 8.6 Blackout would be something in the 160 to 185 grain range. This would achieve a muzzle velocity of around 2400fps depending on the load and barrel length. At this muzzle velocity the bullet will be spinning at nearly 600,000rpm.
As previsouly mentioned traditional cup-and-core bullets are not designed to withstand these extreme spin rates. You begin to quickly run into issues with bullets coming apart midflight, sometimes the moment they leave the muzzle, other times a short distance from the muzzle. This would damage, if not destroy, a muzzle device like a brake or a suppressor. To avoid this, you are limited to loading solid copper bullets which are strong enough to withstand the centrifugal force. These bullets cost a premium.
Which brings up a point a lot of folks overlook. 8.6 Blackout is about as premium as you can get for this class of bullet. It rivals much larger cartridges in cost, and that’s not because somebody mixed gold flakes into the propellant. It’s because the bullets themselves are premium. They’re long, heavy, and often made with specialized manufacturing processes that aren’t cheap. Cast or plated bullets usually aren’t a great match for a 1:3 barrel.
There are other technical reasons you might not want to spin a bullet that fast, like spin drift, but Marc, my editor, reminded me I’m not here to rain on anyone’s parade. He’s right: the intended effective range of this cartridge is well under a mile, and nobody is running it in a machine gun where barrel wear becomes a real concern. Marc’s a good guy. He keeps it grounded.
To his point, and to be fair, the cartridge was designed for one specific purpose: squeeze as much energy as possible out of a subsonic load. The 1:3 twist does exactly that. It performs as advertised by stabilizing long-for-caliber bullets. In theory, you could stabilize a bullet up to 2.7 inches long, weighing north of 400 grains, if you could convince someone to make one.
Where to Buy
8.6 Blackout is still a newer cartridge but there are several firearms manufacturers and ammo makers that offer quality components. Because 8.6 Blackout has not been standardized through SAAMI, there can be some variations in ammunition and rifles that may not produce the best results. It is always a good idea to ask the manufacturer of the ammunition and /or rifle to what spec they are using.
As previously mentioned 8.6 Blackout is a premium cartridge. Thus the ammunition and firearms chambered in it all tend to have that premium price. It’s a great candidate for reloading and the brass is readily avialible.
Gorilla Ammunition supplies premium loaded ammunition as well a virgin 8.6 Blackout Brass, prebuilt bolt action rifles, DPMS Patterned AR10 and AR10 Uppers. They also have barrels if you’re looking to build your own.
Faxon Firearms manufactures top quality AR10, bolt actions, and if you prefer to roll your own, barrels and accessories for the 8.6 Blackout
Brownells carries pretty much everything you need if you want to explore 8.6 Blackout. Barreled Actions, Reloading Dies, Virgin Brass, and complete firearms.
Wrap Up
At the end of the day, 8.6 Blackout is a cool concept, and I still like it. For me, it would be far more useful with a 1:5 or 1:6 twist barrel. You’d get almost the same terminal performance, but you’d also end up with a true dual-use cartridge that handles both subsonic and supersonic loads. That would make it the AR-10 equivalent of 300 Blackout. It would still stabilize the 350- to 360-grain bullets people are selling at a premium, but it would also push more conventional 160- or 185-grain bullets without putting a suppressor at risk.
Developing a new cartridge is expensive and risky. Just the tooling and dies needed for mass production put you well north of $100,000 on the first run, and that probably doesn’t even include tooling for a dedicated 1:3 twist barrel. Q developed it, brought it to market, and marketed it well. Time will tell whether it sticks around or ends up falling short of the staying power 300 Blackout managed to build.
That’s all I have on that,
Jay