What Is the 8.6 Creedmoor?
The cartridge now known as 8.6 Blackout, or 8.6 BLK, started as Kevin Brittingham and Q’s attempt to build a .338-caliber round that could do more than older designs like the .338 Federal. The goal was straightforward: keep the cartridge compact, use a short 6.5 Creedmoor-based case, and make room for long, heavy bullets that can work well in both subsonic and supersonic loads. That combination gives it unusual flexibility for suppressed shooting, short-barrel rifles, and close-to-midrange hunting.
Brittingham originally used the name 8.6 Creedmoor during early development, then Q standardized the cartridge as 8.6 BLK in 2021. The “BLK” name ties it to the .300 Blackout family in spirit, while making clear that this is a different cartridge built around the 8.6mm projectile. Market timing also mattered, since ammo production pressure in the 2019 to 2021 period slowed the launch of any new cartridge that would have needed fresh brass, factory loads, and rifle support.
Brass
Early adopters often formed 8.6 BLK brass from 6.5 Creedmoor cases by trimming and resizing them with proper lubrication and a suitable full-length die. That made the cartridge accessible before factory brass became common.
Now multiple manufacturers like Starline, Alpha and Hornady make brass for it, so fire-forming and die shaping is not necessary anymore and wastes precious barrel life.
Why a New Cartridge
The 8.6 BLK matters because it is not just another neck-up experiment. Its case geometry is meant to carry very long bullets in a compact package, which changes what a short rifle can do.
It supports efficient suppressed subsonic use, while still allowing meaningful supersonic performance from short barrels. That makes it unusual among hunting and tactical cartridges, especially when the goal is compact size without giving up terminal effect.
Building One
Factory rifle options have been limited, although Q and Faxon have both worked toward cartridge support and barrel offerings. Early buyers may need to watch waiting lists or convert an existing platform such as the Fix by Q.
A custom build is also realistic. The cartridge uses a .308 bolt face and fits standard-length magazine geometry, so a properly chambered barrel and the correct reamer can turn a compatible rifle into an 8.6 BLK host. Fast twist rate selection is critical for that build to perform as intended.
Why the Fast Twist Matters
The 8.6 BLK depends on extremely fast rifling twists, commonly 1:4 and even 1:3, because the cartridge is designed around long bullets with a lot of mass. Those twists stabilize heavy projectiles that would be marginal or unusable in slower barrels.
That fast spin does more than keep bullets point-forward. With suitable bullet construction, it also helps drive strong terminal upset, especially when impact velocity drops. The rotational speed is a defining part of the system, not an afterthought.
8.6 Blackout Ballistics & Trajectory
Heavy subsonic 8.6 BLK loads, often 300 grains and up, are built for short-range precision and deep terminal effect, not flat trajectory. They drop fast, drift noticeably in wind, and require real dope if the shooter wants consistent hits beyond close distances. At subsonic speeds, practical shooting distance is limited more by trajectory and wind than raw energy.
8.6 Blackout Trajectory & Drop Chart (Supersonic vs. Subsonic)
Note: Data assumes a 100-yard zero, 1.5-inch sight height, and standard sea-level atmospheric conditions.
| Range (Yards) | 210gr Barnes TTSX (Supersonic) Drop (inches) | 210gr Barnes TTSX (Supersonic) Velocity (fps) | 300gr Sierra MatchKing (Subsonic) Drop (inches) | 300gr Sierra MatchKing (Subsonic) Velocity (fps) |
|---|---|---|---|---|
| Muzzle | -1.5 | 2,000 | -1.5 | 1,050 |
| 50 | +0.8 | 1,910 | +2.1 | 1,025 |
| 100 | 0.0 (Zero) | 1,825 | 0.0 (Zero) | 1,005 |
| 150 | -2.4 | 1,745 | -6.8 | 985 |
| 200 | -6.8 | 1,665 | -18.5 | 968 |
| 250 | -13.5 | 1,590 | -35.4 | 952 |
| 300 | -22.8 | 1,520 | -57.8 | 938 |
Supersonic loads in the 160-grain to 210-grain range give the cartridge a much flatter path and extend useful range significantly. A 210-grain Barnes TTSX launched around 2,000 fps from a 16-inch barrel can still carry meaningful energy at several hundred yards, though it is still not a long-range precision cartridge in the same sense as a .308 Winchester.
The ballistic charts released early on below were later adjusted after more testing. That matters, because real-world velocity from short barrels has to be used when predicting drop and retained energy, not optimistic factory-style estimates.
The 1:3 Twist Rate Explained
A 1:3 twist is extreme by centerfire rifle standards, and the reason is simple, heavy bullets need it. Long 8.6 BLK projectiles, especially subsonic loads in the 300-grain to 360-grain class, need very high rotational speed to stabilize cleanly out of short barrels.
That spin also contributes to terminal behavior when the bullet is built to respond to it. In practice, the cartridge can produce dramatic tissue disruption for its velocity class, especially when the projectile is engineered to expand, yaw, or fragment efficiently. The spin does not replace impact energy, it amplifies how that energy is applied.
Hunting With the 8.6 Blackout
Hunting is where the cartridge makes the strongest practical case. The combination of short barrels, heavy bullets, and suppressed capability gives it a compact field setup that still hits hard on game.
Q has shown the platform taking animals ranging from smaller African antelope to large, thick-skinned species. That does not make it a universal answer for every hunt, yet it does show the cartridge can cover a wide band of game sizes when bullet choice and shot placement are correct.
Barrel Length and Performance
The 8.6 BLK was developed with short barrels in mind, and it remains effective in very compact rifles. Testing has centered around barrels as short as 12.5 inches, and even 8-inch setups have been demonstrated.
Shorter barrels do give up velocity, especially with supersonic loads, so the cartridge should be matched to realistic roles. The strength of the design is that it still delivers useful performance from barrels where many other .338-class concepts fall off sharply.
8.6 BLK vs .338 Federal
The .338 Federal was the obvious comparison from the beginning, since both cartridges use .338-caliber bullets in compact hunting rifles. The 8.6 BLK is the more specialized design, and its shorter 1.685-inch case allows longer bullets to sit correctly for feeding and performance.
The .338 Federal case is longer at 2.015 inches, which limits how well very long bullets can be seated for subsonic use and still feed from a magazine. The 8.6 BLK also shares a .308-sized bolt face and fits .308 Winchester-length magazine systems, which makes rifle compatibility easier.
For heavy subsonic loads, the 8.6 BLK is simply the better cartridge. It handles long projectiles more cleanly, gives more consistent case fill, and is better suited to the role it was designed to fill.
8.6 Blackout vs .308 Winchester
The .308 Winchester still has the advantage when the goal is extended-range supersonic shooting. It has a deeper support base, a broad selection of bullets, and better long-range external ballistics from full-length rifles.
The 8.6 BLK is superior in suppressed subsonic hunting and in short barrels where compactness matters more than raw reach. It was built to launch very heavy .338 bullets efficiently from a small package, and that design gives it a real terminal edge inside its intended envelope. The .308 remains the better choice when distance and flatter supersonic trajectory take priority.
8.6 Blackout vs .300 Blackout
The .300 Blackout proved that a short case can run both supersonic and subsonic loads effectively, and the 8.6 BLK takes that same idea to a larger caliber. It is the bigger, harder-hitting sibling, with far more bullet mass and substantially more terminal energy.
That extra diameter and weight come at the cost of recoil and a much steeper trajectory with subsonic loads. For shooters who want significantly more punch than .300 Blackout can provide, the 8.6 BLK fills that role with more authority.
Trajek for Subsonic Drop Calculations
Subsonic 8.6 BLK loads drop fast enough that rough estimates are not good enough at distance. Trajek is a practical tool for dialing in the steep trajectory, wind drift, and time of flight that heavy subsonic loads demand.
For anyone running 300-grain-plus ammunition at subsonic speeds, a reliable ballistic solver is not optional. Trajek makes the holdovers and elevation corrections manageable when the cartridge’s arc starts to fall hard past close range.
Frequently Asked Questions
The effective range of the 8.6 Blackout depends heavily on the load. With 300-grain subsonic loads, the effective range for hunting is typically around 300 yards due to severe bullet drop. With lighter 160-grain to 210-grain supersonic loads, the effective range extends out to 600-800 yards, though its primary design is for close-to-medium range subsonic performance.
The 8.6 Blackout is better than the .308 Winchester for suppressed, subsonic shooting and hunting because it fires much heavier bullets (up to 350 grains) that carry immense kinetic energy at low velocities. However, for long-range supersonic shooting past 500 yards, the .308 Winchester is superior due to its flatter trajectory and higher velocity.
The 8.6 Blackout uses an extremely fast 1:3 twist rate to stabilize heavy, long subsonic bullets. This rapid twist also imparts massive rotational kinetic energy to the bullet. Upon impact, this rotational energy forces the bullet to expand violently, creating massive tissue damage even at slow subsonic velocities of 1,000 fps.
The 8.6 Blackout is essentially the “big brother” to the .300 Blackout. While the .300 Blackout is based on the AR-15 platform (.223 case) and fires .30 caliber bullets, the 8.6 Blackout is based on the AR-10 platform (6.5 Creedmoor case) and fires much larger .338 caliber bullets, delivering significantly more kinetic energy.
AJ Deysel is a competitive rifle shooter in the PRS and NRL Hunter series, a lifelong hunter, and a recognized ballistics specialist whose load development expertise has been featured by industry leaders like Hornady. He is the founder and lead editor of LoadDevelopment.com. Read more about AJ or view our Editorial & Testing Guidelines.
2450 for 210 gr tsx is pretty fast for a 12.5″ bbl, especially in light of previously published 160 gr barnes going 2500.
Don’t get me wrong. I’m excited for numbers like that! I just want to make sure it’s not a typo, that this is a reasonable expectation.
I can’t wait for this cartridge to come out.
I saw the designer quoted elsewhere that the 160 was running around 2400 and the 210 ttsx at 2000. Don’t know how he came up with 2450 for the Drop chart
THIS. It’s good for people know now that barrels are starting to show up out there that Q’s own load data gets you nowhere near what’s stated in this article. I feel this is just a hype piece that was put out to keep interest up when they were trying to get the development done on this.
I recommend this article be updated as it’s pretty non-factual at this point.
If you’re not going to buy solid copper expanding bullets and actually hunt suppressed at close range, I see zero reason for this cartridge beyond novelty.
This is not a close range only cartridge. That’s just false. I have harvested animals from 9-500 yards with supers and 250 yards (so far) with subs.
Fast twist changes terminal performance with super and and subs and allows you to do things with short barrels and light weight, compact guns never really done previously.
twist rate can only do so much… you still need barrel length to accomplish velocity because you don’t have time to get powder to burn fully. You may be able to harvest out to 500 yards, but, if this is a shortened .338 Federal, then it’s still lacking compared to a .300WSM which beats .338Federal at the same 500yd mark with less drop, more velocity, more energy, way less wind drift, and a faster flight time… this really seems like someone came up with a cartridge to solve a problem that didn’t really exist…
Practical velocities from the 12” are about 2100-2200fps with 160-210gr. projectiles.
Is there an estimated time frame to be able to purchase the 12.5 barrel to convert the AR-10 platform?
If possible, is there a way to get on the pre order list?
Gorilla ammunition is taking preorders on rifles/pistols now.
I’m ready to change my old AR10 and this looks like a cartridge that I’m going to love. Timing?
AWSOME!!!! I have been holding out on purchasing a hunting semiauto for the best hunting and protection rifle and you have just provided the most versatile round out there for hunting. Simply Amazing. thanks v/r
Can you show us these speeds chronograph old guys like me would love to see that out of short barrel thanks
So,
I love the 338 Federal, I don’t see how you are getting the velocity you quote out a 12.5 inch barreled 338 Savage, I’ not saying I doubt you, just don’t know how your doing it unless you are using Superformance technology which means handloaders will be disappointed.
What I really want to know is, how on Earth did you find a PH that would let you kill a Cape Buffalo with a low power 338 Federal carbine? No amount of “magic barrel twist” will make that be something that you should do.
I get it, you need it to fit in an AR mag, and the 338 caliber is great, but we really do need to think about responsible advertisement.
Fast twist is using more available energy. I’ve killed 4 Cape Buffalo with 8.6blk with 10”-16” barrels. It’s efficient.
And when developing new technology, eventually, someone has to field test what the math, computers, and gel tell you.
He did not invent 300 blackout. Research the 300 2hisper, or just read the first couple of lines on wikipedia.
*300 whisper
They aren’t the same.
210 bullet at 2450 NO, just saw the load they been using and it is a 210 grain bullet at 2000 fps , huge difference so big in fact if this turns out to be a fact I would not get one
NO, this is not true , a 210 barns is only going 2000 fps with the 8.6 Blackout , which is not good, subsonic seems to the real only use for this round
Fast twist, rotational velocity is the benefit and what you are missing. Makes 12” 8.6blk more effective than 16” .308win.
Maybe a 180 gr. at 2200 fps, if your lucky. Overhyped bigtime.
This is marketing is nonsense. 338 federal can be hand loaded to subsonic velocities with heavy bullets.
“More consistent powder burn” is a farce as the parent case is the same diameter as all of the .308 family.
Simply a less powerful version of 338 federal. This is 44 special compared to 44 magnum. The only advantage would be commercially produced subsonic rounds. Which is no advantage over 338 federal. 300 blackout succeeded because of the anaemic kinetic energy performance of 5.56. A .308 Winchester doesn’t have that problem, and there wasn’t a dire need to slow down a heavier round for increased penetration.
338 Federal Velocity (1st#) and energy (2nd#)compared
Muzzle:
300 WinMag (180gr)- 2960/3502
35 Whelen (225gr)- 2600/3377
338 Fed (200gr)- 2700/3237
7mm Mag (160gr) – 2950/3091
30-06 SPFLD (180gr)- 2700/2913
308 Win (165gr) – 2700/2671
100 yards: zero
300 WinMag – 2701/2915
35 Whelen – 2351/2761
338 Fed – 2487/2746
7mm Mag – 2752/2691
30-06 SPFLD – 2512/2523
308 Win – 2501/2291
200 yards:
300 WinMag – 2456/2411 -3.3”
7mm Mag – 2563/2333 -3.1”
338 Fed – 2284/2316 -4.1”
35 Whelen – 2116/2238 -4.9”
30-06 SPFLD – 2332/2174 -4”
308 Win – 2310/1955 -4.1”
300 yards:
7mm Mag – 2381/2014 -11.5”
300 WinMag – 2224/1978 -12.3”
338 Fed – 2090/1940 -15”
30-06 SPFLD – 2160/1865 -14.5”
35 Whelen – 1895-1793 -17.3”
308 Win – 2128/1660 -14.7”
400 yards:
7mm Mag – 2207/1730 -26.1”
338 Fed- 1905/1612 -33.6”
300WinMag – 2005/1607 -28.4”
30-06 SPFLD – 1995/1591 -32.4”
35 Whelen – 1690/1428 -39.9”
308 Win – 1954/1399 -32.9”
No. Calculate 1:3 twist rotational energy. And you can’t get subsonic accuracy with slow twist.
What reliable expanding bullet is there in the market for the 0.338?
Lehigh don’t make any 0.338 subsonic specific anymore..
Hornady subx and gmx, Barnes, Discreet, Makers, etc. Most existing bonded and solids work perfectly.
What about hard cast/HTC coated projos?
338 Federal has already suffered from the lack of .338 Projectiles that expand reliably at its velocities. How is this round, which is even slower going to magically do better?
Fast twist. Fits in mag.
Why is this better than a 450 bushmaster? The 450 fits in an AR-15 platform and actually can fire a 200 grain bullet at 2500 fps. I get that ballistic coefficient is probably really good for the 8.6, but so good that starting out 400 fps slower doesn’t even them out? Is it the crazy twist rate? I mean what does it do that an AR-15 big bore cant, why should I buy one? Both bullets are going to drop like rocks at distance.
Yeah and the 300BLK was poised as the greatest Hog Hunting round ever in all the Gun Magazines.
You couldn’t convince the fanboys and casuals otherwise that they bought a .30 carbine.
We see how that turned out. 300BLK sux for hunting outside 75yds.
I don’t see how this new 8.6 trumps a .308 other than its ability to be a little more effective when going sub sonic. You can run a .308 with 220gr match kings or game kings at 1000fps and do fine. Switch to match ammo and hammer out to 800 yds or better.
It sure doesn’t beat 308 on being versatile and ammo availability.
But more power to him if he can sell a new system. Marketing genius.
Barrel change only. Supers and subs. Full mag capacity. Reliable. Distance. Accuracy.
What barrel length is optimal shooting suppressed in the 8.6 cartridge? I would think a 16” would be quieter, but this round appears so unconventional I don’t know what think.
I definitely want one. I already have a couple of their guns, a Honey Badger and a Mini Fix both in .300 Blackout. A couple of decades ago I used to shoot a .300 Whisper a good deal and really liked it, so why not. JD Jones has come up with some great cartridges over the years but he never really, in my opinion, carried them through to their place in history like Q has done, and now that they have the 8.6mm Blackout it looks like I’m forced to spend more money. 😎
1:3 or 1:4″ twist? I asked this on the Firearms Blog and I was told to look at the video linked above. The ‘super spinny’ bullet hits centre of the block where its expansion can be fully seen and as such its expansion is mostly undisturbed. The normal spin bullet hits almost the bottom of the block, where its expansion cannot be fully seen and its expansion is highly disturbed by the table. This has got to be one of the poorest examples of a difference I seen in a long time. Plus, these are very light for calibre 140 gr projectiles, so these do not exactly sound normal
As to a required twist rate for stability, with a 1:10 twist, at +69F (+21C) 1,070 fps (326 m/s) a 300 grain (19.4 g) Sierra Match King is just ‘gyroscopically’ stabilised, with a stability factor of slightly greater than 1.4. A 1:9 twist gives more than adequate stabilisation of about 1.76 at the same muzzle velocity. Even with 300 gr all copper bullets like the Cutting Edge Lazer, this can be adequately gyroscopically stabilised at subsonic velocity with a 1:8 twist, with a 1:7 being better.
I can see that this higher spin may be advantageous in that the extra spin opens up and breaks off the petals of mono-metal subsonic projectiles? But over gyroscopically-stabilising projectiles can lead to no end of accuracy problems. This such as it the projectile being gyroscopically stable, but dynamically unstable, and that the projectile can no longer able rotate around its centre of gravity to its nose follows the ballistic trajectory, i.e., the tractability problem. This is even more problematic when firing anything at supersonic velocities.
As such I’d like to see the downrange accuracy of these over-stabilised bullets and a proper comparisons of projectiles hitting gel blocks, as at present this all looks and sounds like marketing rubbish too me. Personally, I’d much rather have a correctly technically (ballistically) designed rifle with a barrel that has twist rate that adequately stabilises the bullet and does not potentially cause accuracy problems. Though the daft 1:3/1:4 twist rate may give a bit of an improvement in the terminal ballistics of mono-metal projectiles, I’d rather something that can hit a target at all ranges. It would be far better to simply use (develop) better-designed mono-metal or thin-jacketed lead alloy core bullets that expand at low velocity and normal spin rates than use this over-stabilisation method to supposedly improve terminal ballistics.
Best answer yet. I purchased the AR-10 barrel for a Palmetto State Armory PA65 I have in my inventory. After working through many loads, and dealing with brass issues (turning necks ) I’ve come to the conclusion that this is the most complicated cartridge ever designed. What other cartridge has to match ammo to the barrel length?
I’m new in this game with 8.6 blk and trying to find out how much powder of 1680 accurate I shout try with 300gr sierra bullet and 285 gr bullet from gorilla ammunition? Any data would be helpful. Thank you all for help.