Is 300 AAC Blackout the New Black?

CMG 300 AAC Blackout rifles (courtesy The Truth About Guns)

Regular readers no doubt know that our man Leghorn is deeply enamored with 300 AAC Blackout (a.k.a. 300BLK). Back before the round was making the rounds, Nick was singing its praises and predicting a glorious future. The future is now; plenty ‘o gunmakers are making rifles and barrel conversion kits to accommodate the cartridge. CMMG offers five rifles chambered in 300 AAC Blackout (the four above and one more besides) and three barrel options for DIY gunsmiths. In case you’re still not convinced (general ammo availability issues aside), here’s CMMG’s pitch for 300 AAC Blackout . . .

The 300 AAC BLACKOUT (7.62X35mm), or 300BLK, offers increased energy delivery and knock-down power in the same package as a 5.56mm AR-15 rifle. By utilizing a 30 caliber projectile, a wide range of loads are available in the 300BLK caliber for shoooters to tailor the round to their specific needs.

Whether you’re seeking a high-powered sub-sonic solution for suppressed fire [ED: now that’s what I call poetry], or an impressive brush gun, the 300 AAC BLACKOUT should be your caliber of choice! The 300BLK round only requires a different barrel as the rifle uses the entire 5.56 AR-15 platform to function.

You in?


  1. avatar Chris says:

    Really want to get a Mossberg MVP with a threaded barrel in 300 AAC.

  2. avatar Ralph says:

    I’ll buy some 300 AAC Blackout the next time I see some in my LGS. The same goes for 5.56 NATO and 9mm Luger. And 7.62 NATO, .40 Cal. and .38 SPL. Oh, and let’s not forget .22LR.

    I miss them all. Sniff.

    1. avatar tdiinva says:


      I will continue to use the less popular 243, 30-06 and 45 ACP. No ammo shortage in those calibers.

      1. avatar Pulatso says:

        There is in .45 around here. I’ve been planning on getting a .45 this summer, and I’ve had a hard time finding much locally, just a box here or there.

      2. avatar Tim U says:

        No .45 shortage? What world are you in? We can’t keep it around here.

        I miss ammunition period…. the only stuff you can buy in my location is shotgun shells and the expensive hunting ammunition in larger calibers.

        1. avatar tdiinva says:

          My local Dicks always has a good supply. I always pick up a box or two when I am in the neighborhood

      3. avatar Dr. Kenneth Noisewater says:

        I wish you’d tell my local Wallyworld that there’s no .45ACP shortage.

      4. avatar Carry.45 says:

        Ha. But you support dicks to do it. A wise man once said, “Fvck that”

        1. avatar tdiinva says:

          Back in the bleak days of December I stated my position on why I would continue shopping at Dicks.

          Unlike Cheaper than Dirt, Dicks is a sporting good store that sells guns, not a gun store that sells other sporting goods. They never stopped selling guns and ammo. They stopped selling center fire ARs. I will give them the benefit of the doubt because they have to balance a larger than gun owner customer base. But I tell you what, thanks for boycotting. Maybe that’s why I get all 45 I can use.

        2. avatar Carry.45 says:

          I get plenty at Walmart. And they tend to have value packs. I’m all set with a company that helps demonized the most popular rifle in America.

        3. avatar Cleophus says:

          Carry.45 says:
          “Ha. But you support dicks to do it. A wise man once said, ‘Fvck that.'”

          You’re right, Carry .45, “tdiinva” is bad wrong. It’s because of sellouts like him that turncoat stores like Dick’s are able to remain in business. Fvck “Dicks,” and fvck the sellouts who still deal with them.

        4. avatar Matt in FL says:

          If you’re going to be offensive, don’t be a p*ssy about it. Don’t say “fvck the sellouts who still deal with them,” say “Fvck you, tdiinva.” Because that’s what you’re really saying.

          Better yet, don’t hide behind your keyboard. How about you go down to your local Dick’s Sporting Goods — you don’t have to make a special trip, just when you happen to be in that plaza next — and say “Fvck you” to every person you see walking in the doors. I mean, they’re all sellouts, after all, right? If they’ve got their kids with them, don’t let that stop you. Those kids need to learn that their parents are sellouts with no moral character, and now is as good a time as any.

          Oh, no? That’s too far? Or too much trouble? Or you simply don’t have the balls? Then shut the f*ck up about it. Have the courage of your goddamn convictions, or keep them to your goddamn self.

        5. avatar Carry.45 says:

          Matt you have no idea what you’re talking about. Not everyone who shops there are gun owners. So I may not even be saying f you to gun owners. And don’t talk about my balls. My wife is plenty happy with the both of them and what came from them: our son.

        6. avatar Matt in FL says:

          Well, my comment was really directed at Cleophus, but I suppose it applies to anyone with his internet attitude. People talk a lot of smack here, but few of them would ever dare back it up in real life.

          As for the Dick’s customers, does it matter if they’re gun owners? Shouldn’t everyone boycott them for their actions? Why should only gun owners not shop there?

        7. avatar Carry.45 says:

          The lat time I was in dicks was whenthey pulled the ARs from the shelves. The last thing I said to dicks was thanks for selling gun owners down the river. I haven’t been in there since.

          As to why non gun owner shouldn’t shop there its because they’re not gun owners and they’ve probably already made up their minds on guns. standing outside saying Fvck you to all these customers going inside may serve to turn off people to guns who at one point had no opinion on them one way or another. Bad idea.

        8. avatar Matt in FL says:

          “…may serve to turn off people to guns…”

          That’s fair. And besides, the whole thing was hyperbole anyway. I never for a second thought that anyone would follow through on my suggestions. But then, that was kinda my point.

        9. avatar tdiinva says:


          If gun owners boycott Dicks then they will still be in business because guns are pretty much a sideline. That is my point. Dick’s is a business and they make decisions that they feel will help the maximize there profits like any business should. If they feel that selling centerfire ARs is bad business then they won’t carry them. I don’t blame. On the other Cheaper than Dirt’s entire business base is made up of gun owners. I hold them to a different standard. If they screw a subset of the gun community they screw all of it. I don’t shop there any more. I hate political correctness from which ever side of the political spectrum it comes from. So in the spirit of this thread “up yours” (said with a friendly smile.)

        10. avatar Pat says:

          Dicks suck dicks. Not selling ARs no more was weak sauce (caving in to anti-liberty libtards).

    2. avatar Accur81 says:

      Word. The 300 AAC is a caliber that is easy to shoot a lot of (well, judging by what I’ve read) but pretty damn difficult to buy a lot of. Since I didn’t stock up before the last mass murder in a gun free zone, it’ll be exceeding difficult at this point.

      1. avatar sdog says:

        indeed, i would say the same goes for 5.7×28. All i see in the store these days is hollow point in hand gun calibers (not the most cost efective way to train). online is the only way that i see for the time being.

  3. avatar KeithF says:

    I’m in

    18″ Wilson Combat barrel on a RRA upper with free float. 51T Muzzle for when I get a can… need ammo! (Holding on to my last 60 rounds of Hornady 110gr)

    1. avatar k4R-15 says:

      Have you calculated the drop at 200 yds or farther? I’m curious to know if the 18″ barrel lessens the drop after 100yds

  4. avatar k4R-15 says:

    Confirmed: I am a satisfied user for about 1 year now.

    It works as advertised although the factory ammo I purchased was too short to feed reliably. I load my own supersonic (155gr FMJBT) and subsonic (220gr HPBT and 178gr AMAX) rounds and with some tuning of the cartridge length have zero problems. Recipes are on my site if you’re interested.

    The main attraction to me is that this is an alternative caliber that runs with all the standard 5.56 AR components except for the barrel (although its less hassle to just buy a dedicated upper for the BLK). It’s very flexible and cost effective that way.

  5. avatar Tod says:

    I just sold my CMMG 300 BLK upper when ammo went over $40/box before shipping. I haven’t seen 300BLK ammo in stores for months, while most everything else has been slowly coming back around here.

  6. avatar Chris says:

    I will consider getting an upper in .300BLK when I move to a free state and can have a suppressed SBR.

  7. avatar Tom in Oregon says:

    Love mine. As an excercise in potential futility, I started building one in January. Finished in March for about 850 bucks.
    Learned how to make my ammo watching Mr. Leghorn on youtube.
    Called up Barnes bullets in Utah when all the websites had no projos. Ordered 500 rounds and they were here in 5 days. Scored 1,000 147 grain from Pat’s.
    This is a kick butt round!
    Haven’t started experimenting with sub-sonic loads yet. Hitting my foot square plate at 400 yards with no problem.
    Love it.

  8. avatar Don says:

    Just got into the AR15. Do you guys tend to own a lot of complete AR15 rifles in different calibers, or lots of complete upper assemblies that you switch on a smaller number of lowers?


    1. avatar Mike in NC says:

      For some, ARs seem to assemble themselves, growing from spare parts collections into complete rifles. Having a collection of uppers and one lower will certainly work, but it won’t take long before you have a collection of complete rifles.

    2. avatar Matt in FL says:

      I have two lowers (my first) in the process of building out right now, and my expectation is that I’ll end up with two complete rifles plus one extra upper in the next couple months. Beyond that, who knows?

  9. avatar AZRon says:

    I still have my tactical Betamax machine for sale at a friendly price.

  10. avatar Jeh says:

    In? Absolutely, that is if I can make my barrel 11.5inch, but I don’t think the ATF will stop being paranoid anytime soon.

    1. avatar CA.Ben says:

      Two words. AR. Pistol.

  11. avatar B says:

    Have a DSArms 300 BLK upper on backorder. Also have reloading dies, brass, and primers ready to go. Wish I’d bought more of those CCI primers on backorder though, things are double what they were in December. Haven’t seen any commercial Blackout on sale for months either.

  12. avatar Sol says:

    noob question so please don’t flame me. when you say that it works with standard AR-15 gear except for the barrel does that include magazines???

    1. avatar utdmatt says:

      Yes, it’s pretty much using re-sized 5.56 cases, so most everything that goes in the lower of the rifle can be used for both (magazines, triggers, etc).

      1. avatar Sol says:

        thanks everyone. looks like i have two new types on my list now…a TAVOR and a 300 blk out…

    2. avatar Ralph says:

      @Sol, relax. You’re among friends. Nobody ever gets flamed here for asking an honest question.

    3. avatar Robert Farago says:

      As Ralph says (and knows from personal experience), no flaming allowed on TTAG. If you see any please send the link to [email protected]

    4. avatar Nate says:

      Literally EVERY part of a standard .223/5.56 AR-15 is compatible with .300 BLK, except the barrel.

    5. avatar crosswiredmind says:

      Some magazines work better than others. I have found that Gen 2 Pmags tended to allow the second round in the stack to slip out. The Gen 3 Pmag works great, as does the Lancer L5 and the Troy Battle Mag. GI mags work if they have the right kind of follower. D&H now make a 300 BLK specific mag, but I have not tried one yet.

  13. avatar Nate says:

    I am still shopping for a folding stock SBR in .300 BLK, preferably 18-20″ OAL folded, to use as a suppressor host. Any suggestions?

    1. avatar WA_2A says:

      I don’t know, it sounds like a good idea. However if you want advice on the build send it over to me when you’re done so I can, uh, evaluate it…

    2. avatar Marcus Aurelius says:

      This might be helpful. Not sure where I first saw this, it may have even been here. I’ve been an insomniac lately, so every once in a while I pull an all-nighter to re orient my sleep patterns. So my memory is a but fuzzy today. Anyway, it allows you to put a folding stock on an AR.

      Anyway, I apologize if it was mentioned on a post here already because that is likely where I got it from.

  14. avatar Billy Wardlaw says:

    Now if only I could find a decently priced, quality gas-piston upper in 300 AAC.

    1. avatar crosswiredmind says:

      My understanding is that 300 BLK runs better with direct impingement. I have heard that this is especially true for sub-sonic loads and suppressed use.

    2. avatar Human Being says:

      Not a whole lot of piston excitement for 300 Blackout because if you fit a suppressor, you end up with fouling in the chamber anyway. That kind of defeats the purpose of the piston in an AR-15.

      Blackout is what made me Stop Worrying and Love The Direct Impingement.

  15. avatar Pulatso says:

    Two things I’ve learned in this shortage: you can never have enough calibers/caliber options from your arsenal and popular stuff, rather than being easy to find due it’s popularity, dies up just as quick and hard, if not quicker and harder, than everything else…except for certain rifle calibers. No 5.56 or 7.62×39, but plenty of 6mm, 7mm, 22-250, and 30-06 around here, and one store in particular store that always has 300 Win on the shelf. I need to expan my rifle collection.

  16. avatar Shenandoah says:

    Not until we see a dramatic drop in price and a rise in availability. Right now it’s like paying for 93 octane fuel vs 87 octane. There might be some performance benefits in the Super, but for a daily driver the Regular (5.56) gets the job done just fine.

    1. avatar Human Being says:

      Make your own; the components are common.

      1. avatar Accur81 says:

        Yeah, but the components aren’t.

  17. avatar 2Savage says:

    This is a really neat caliber. Bought a Daniels Defense last fall and took it to TX for a deer hunt. Was shooting Barnes 110 gr bullets. A 12 and a 15 point were both DRT. Like all Barnes bullets, perfect mushrooms.

  18. avatar mike says:

    Too bad there’s no ammo available. Probably THE hardest to find of all the common calibers.

  19. avatar ht4 says:

    Those don’t look like 300BLK guns. The gas system is too long on a couple of them. There is no way that the bottom gun will cycle subsonic loads.

    1. avatar crosswiredmind says:

      In order to effectively cycle subsonic loads the gas system should be pistol length, or carbine length with a suppressor.

  20. avatar John Bergmann says:

    Finishes my blackout gun a few weeks back. Not a lot of ammo but I am looking at reloads.

  21. avatar Sixpack70 says:

    I’m in once I move to Kansas. I have two stripped lowers. One will be a regular 5.56 build and the other will be a .300BLK build. I will probably end up making my own ammo so I can feed the gun. Everything I have seen on the round has been impressive. I might even go crazy and try to get a suppressor.

  22. avatar Blehtastic says:

    If I ever get an NFA trust drawn up, a suppressed SBR in 300 BLK will be my first project.

  23. avatar Ensitue says:

    NO ammo here and DHS is traceing mail orders

  24. avatar Ensitue says:

    I don’t know about you but I have heard that PPL who hve been preparing for the comming melt down recomend COMMON ammo

  25. avatar Joseph says:

    The 300 Blackout will enjoy a bright future and will likely displace the 6.8mm SPC in popularity. While the 6.8mm SPC is generally ballistically superior, it requires an incompatible bolt and magazine. While an incompatible bolt isn’t too big of a deal, incompatible magazines is a big deal. Aftermarket support for 6.8mm SPC magazines appears to be very limited compared to the support for .300 Blackout, which is equal to 5.56x45mm by design.

    1. avatar Accur81 says:

      6.8 ammo is hard to find also, and I think it is a much better hunting round, with less limitations, than the 300. Those advantage should be enough to ensure the future of the 6.8. Still, using stock AR parts, 5.56 brass, and .308 bullets is a massive advantage. You can actually go to Silver State Armory or Palmetto State Armory and get 6.8 for $22 / box. 300? Not so much.

  26. avatar Ensitue says:

    The 300 offers nothing that my opressed 30-30 cannot deliver (in spades) and I’ll never be short of ammo

  27. avatar J says:

    I think the 300 BLK is the only non 5.56/.223 AR style rifle I’d ever buy, only because it uses 5.56/.223 mags. The 6.5 and 6.8 don’t and I don’t want to mix a handful of 6.X mags with my collection of 5.56 mags and get all confused.

    Acutally, the rifle I have wanted (and can’t seem to find) is the S&W hunter becuse I takes both .300 BLK and .300 Whisper.

  28. avatar AbsintheAnderson says:

    The .300BO is most practical with a suppressor – as it’s very quiet and effective. Supersonic, it’s a more expensive alternative to 7.62×39.

  29. avatar Tim says:

    Bought a CMMG 300 AAC Blackout a year ago and with an AAC can, it shortstrokes using Remington 220 grain subsonic ammo. Would eject the spent round but would not blow back far enough to strip the next round off the mag and load it into the chamber. Tried to get help from CMMG but all they would do is tell me that their 300 Blackout didn’t like the Remington ammo. In my humble opinion, that’s pretty sorry- building a gun that won’t operate properly with the most common ammo on the market. Under the circumstances, I will NEVER buy a CMMG product again. If any of you have suggestions to make this gun work with the Remington ammo, they would be appreciated. I’ve already tried a heavier buffer without success. I don’t want to enlarge the gas port because higher pressures will result when shooting supersonic ammo. I’m thinking about cutting little bites off the recoil spring to hopefully find a point where the Remington 220 will cycle properly. Have I tried other manufacturers’ subsonic ammo? No, because none has been available.

    1. avatar Jason says:

      Why not try a “lighter” buffer for the remington ammo, they sell them for “competition” guns. Could solve your problem, it’ s a cheap solution. Or just send me all of your remington ammo, it shoots just fine through my AAC with a Huntertown can….

    2. avatar Marcus Aurelius says:

      Yeah, a lighter buffer would be beneficial. Also if you had to open up the gas port you could probably find a manufacturer who makes an adjustable gas block for a DI gun which would allow you to constrict the gas pathway again for the hotter super sonic ammo.

  30. avatar George says:

    Anybody selling any .300 AAC Blackout ammo between 110 and 150 grain and not at the ridiculous extorting prices I see on the net?

  31. avatar Tim says:

    I own one in 300 blk and love it. I reload my own by cutting down the .223 brass.

    So no shortage here!

    That will also take care of the remington issue the other guy has. you can put what you need for powder. the remington is probably a little light in the powder.

    now 22lr thats a different story. thats been a shortage. lol

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