Another Strike Against The 300 Blackout

Our regulars know that, at least for the foreseeable future, we want nothing to do with the 300 Blackout cartridge. Yes, I am aware that it is the flavor of the day. Yes, I am aware that it’s optimal for suppression. Yes, I am aware many say it preforms like a 7.62×39 but in a AR.

Sure. Sure. Which is all good. But none of those things are mutually exclusive to the 300. And on principle, I am not opposed to switch caliber weapons. I run both a Blaser R8 and a Blaser Tactical 2 rifle. Combined, I believe there are over 40 calibers available between them.

But one of the selling points of the 300 Blackout is one of it’s drawbacks. The standard AR bolt and magazine work for both calibers. At least on the Blaser system, you have barrels, bolts and magazines that all need to make sense. And there is a clever way that Blaser presents the markings for all three parts in one field of view.

On the AR, it is very, very, very easy to simply pickup the wrong ammo and fire it in the wrong gun. With catastrophic results. Yes, I understand it’s a training issue. Yes, I understand it’s a user error, not a design flaw.

But 300 Blackout doesn’t do anything for me that standard calibers don’t. So I choose to not mess with it. Just in the last 15 or so years, I have seen 357SIG, 10mm, 45GAP and 6.8SPC statistically die. With what appears to be 40S&W shuffled off to Hospice Care. And I’m skipping over more calibers that in reality never got out of the wildcat stage.

300blk has a long, long, long way to go before I let even one single, solitary round into the arsenal.

“Shooting Guns & Having Fun”

Marky Mark

Marky Mark

Writer at
Writer for Co-Host of the John1911 Podcast. Video content provider for John1911-TV.

Areas of focus: Defense and National Security, Modern Light Weapons, Analysis of the Geo-political / Military Relationship in the Context of Strategic Goals.
Marky Mark

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  • Chris Bergen

    Yikes… What’s the story? A 300 blackout in a 5.56 barrel or vice versa? My 300 BLK OUT is well marked AND is a different length than my 5.56 (10.5 vs 16), so hopefully it will be obvious enough. But the lesson is well considered…

    • 300 in a 556. Hence the massive damage. It’s something the 300 guys, who run a conversion, need to at least be made aware of.

      The biggest offender is the guy who shows up at the range with both. And then has friends with him as well.

      Both calibers on site. People are talking. Possibly shooting each other’s guns.

      Accidents happen.


      • Chris Bergen

        Out of curiosity, I tried to load a 300 blkout into my 5.56 rifle… The bcg would NOT go into battery, which of course means it won’t fire… I suspect something else may have happened here…. Now a 5.56 will certainly feed into a 300 BLK chamber…

        • Chris Bergen

          You can see the scratches from the lands on the bullet…

          • Look deeper into the subject.


          • Chris Bergen

            Apparently if I had allowed the bolt to go forward with full power it would have pushed the bullet into the case (setback), allowing the bolt to go into battery and let the hammer hit the firing pin. While it’s certainly possible, that’s a whole lotta things to go wrong… Hopefully I won’t be sending you a pic of mine!

          • Correct.


      • right_on

        How did the bolt even close? 😳

        • Jim

          repeated blows to the forward assist with a mallet.

          • right_on


        • Known issue. 300Blk loads vary greatly by bullet weight alone.


  • Disappointed

    Wtf did I just read? By your argument if I had identical looking .223, .243, and .308 Rem 700 rifles then I would blow them all up because I’m not smart enough to understand which is what.

    If you truly believe this is a downfall then you really need to educate yourself on firearms. Between you and Wayner at TTAG I am now dinner for reading articles on the Internet.

    • Tony Filipeli

      I got out of it….a personal opinion to the “look” of similar pieces and the user failing to identify prior to firing the weapon. More about user error versus weapon error.

      • Which is fair. As long as the owner, and everyone around him, are aware of the issue we are all better for it.


    • I don’t know who Wayner or TeeTag is, so please tell him I said hello.


      • Mikial

        TeeTag is the snarkiest forum of internet gun ‘experts’ you’ll ever have the dubious entertainment experience of reading.

        • Well, it’s a forum so that explains a lot. Forums are good for “some” pieces of data but tend to be way too political and drama oriented. I like to spend my time outside. I realize I am in the minority though. –Marky

  • charles robb

    Blazer R8 is not immune to operator failure. I have a customer who’s missing 1/2 his face due to a Blazer R 8 failure!💀💀💀💀💀💀💀💀💀💀💀💀💀💀

    • I agree. No it is not. Caliber conversions for any gun introduces new issues. And we need to educate the user before he blows a body part off.

      Send me the Blaser R8 info. I would like to see it and post an article about it. E-mail is fine if you prefer and I can blur and hide identities.


  • JphilB

    This is NOT a reason to stay away from buying a 300 Blackout. This is like not buying a diesel truck because you are afraid you will put gasoline in it and wreck the engine. “Another Strike Against Diesel!!”

    • That is a GREAT point actually!!!!

      Just like with diesel vehicles in the US, you need to tell the average buyer that he or she will need to pay closer attention to the gas pumps. And explain that you may pull up some pumps and find no gas available for you.

      Also if you let someone borrow your car, or have them fill the tank while you hit the head, make sure they are aware they can’t grab premium 99 and put it in your six figure European car.

      Man! That is actually EXACTLY the point. Thank you.


    • Lincoln Pope

      I need to learn to read other posts before I comment.

  • TheRealHorridus

    I personally think you are missing out…….

    [[overly long fanboy essay white knighting the .300blk REDACTED]]

    ……..Don’t blame a caliber for someone not paying attention 🙂

    Love your shirts!

    • Look, like the rest of you I live in the real world. I would love to shoot every caliber of every gun ever made. But in the real world, I am limited by logistics and money. I like to shoot quite a bit. If I ever did run 300blk, it would have to be more as a precision rifle. If money was of no concern, maybe I would be of a different mind. But I recall some years ago running into a well known gun-mag professional who was running 6.8. It was the greatest thing since sliced bread. And he has the inside dope that the SF guys were going to pick it up. In the end, he fired I think over 1000 rounds of 6.8 at $1 or $3 a shot! And Big Army never came calling.


      • DChrls

        300 Blackout isn’t what I would consider a precision round; not that I’m some expert on the subject.
        If you want to shoot precision long distance in an AR15 and use off the shelf/commercially available ammo look at .223 or better yet 6.5 Grendel. If you reload there are more rounds available for the AR15 that are accurate at long distances.

        • Guess I should explain. I know a civilian SWAT sniper who bought a 300blk bolt gun. His argument was for urban deer deprivation. But when he went out to use it at even moderate distances…they had all kinds of trouble.

          I guess I should have specified “bolt” as opposed to automatic. 30 rounds of 300blk adds up quick on the expense report.


  • Daniel, God is my judge

    Man, I am so old school. My SHTF rifles are 5.56 ARs, 7.62×39 AKs and an LAR8 308. No way are you going to interchange ammo or magazines. BUT THEN, I got to thinking about whether the Colt 1911 9 mm magazine would fit into the Kimber 45 auto, both are officer models, 7 rounds. Surprise, it will and when the slide goes into battery it even picks up a 9mm round. But, I laughed my a.. off when I tilted the gun down and the 9mm round slid out the end of the barrel, guess that ain’t gonna go bang. I still believe in the KISS principle. Thanks for the insight Marky.

    • It’s the Walmart principle for me. In MSR / Tac Rifles, I look at even 7.62×39 as a non-standard caliber. Why? I live in the United States! 300Blk? In a MSR that I use like a MSR? Pass.


      • Mikial

        Have to agree with you here. Yes, we do have an AK 7.62X39 rifle because . . . well, because we wanted one. And we have a Mosin in 7.62X54r, because I wanted one. We have ammo for both and enjoy them. But for SHTF items we stick to common US calibers like 5.56/.223, 30-06, .308 and the common pistol and revolver rounds like 9mm, .45ACP, and .357. Of course, 22LR is always included. I tend to shy away from anything I consider ‘exotic’ because I don’t want to have to worry about ammo availability.

  • Thomas Jeffer

    Well I can’t say one way or another on this topic right now, I like the 223/556 case and enjoy the ar platform so I said to hell with it and I bought a 16″stoner barrel in .300 blackout cause I had some extra parts including an upper and lower so I spent the $89 from midway and ordered it and a set of dies just to please my curiosity, still haven’t bought a BCG yet but I will.

    so far from what I can tell its a lot of prep work getting brass ready if your converting the 556 down to it and 556 is already a pain in the ass to load after swaging and trimming blah blah blah, but fuck it I’m anxious to see what the thing will do with a can on it, BUT i joined a .300 blk page on Facebook just to see if I could find some load advice ya know and ask some questions and what I find is these guys act like this cartridge is gods gift to human beings and right there I was just dumb struck to hear some of these guys pushing bullshit of how the blk out round is harder hitting than a .30-30 and it’s better than the Russian round and how if they were going to buy a bolt gun it would be blackout over other cartridges, instantly I call bullshit to these guys and pretty much call them out on almost everything and tell them that in my book the only Beautiful thing of it is to me is that it takes the AR mags and the bolt as well and it’s a caliber I can hunt with in my state not that it’s the rifle I’m gonna grab to go tag a buck but if I wanted to I could, but it’s not that crazy of a round.

    these guys acted like I just kicked there dog right in front of them hahaha whatever, I like the idea of the round but I completely understand your stance on it about not adding another cartridge to buy and stock up on it cause it’s expensive BUT I do have to say that just because it’s a different oddball cartridge don’t let that detour you on guns,some of my most favorite guns to shoot are oddball/old calibers such as the .32-20, love the hell out of that round I don’t shoot it even an 1/16 as much as any of my other guns, it’s expensive and not easy to find the rounds but I like it, a lot of guys could talk shit about how a 9mm is harder hitting and all it’s a better round but I really don’t care I like it,

    the .300 blackout would not be my go to/ shtf rifle. but in my book every gun is worth owning even if you don’t shoot it as much as other guns.

    I really enjoy the podcast guys, keep up the good work

    • You probably get the award for the best comment of the thread and one of the best ever posted on the site. You have the right attitude for 300blk. It does do some stuff good, but for most of how I run a AR/MSR style rifle, 300 is just pissing money away.

      It’s like 10mm. I like it. It has it’s place. But I recall having a 10mm conversation with a retired US Marshall friend of mine and some of this thinking and logic was coo-coo.

      I call it bias. And when you realize that most American gun owners have their ego wrapped up in their gun purchases, it gets personal real quick. And when things get personal, the bullshit meter gets turned up to 11.


  • StraightShot

    You are saying that this was caused when a shooter chambered (partially) a .300blk in a 5.56mm rifle?
    If that is what happened I need to wonder how the got the rifle to fire as the 7.62mm diameter bullet should not fit far enough into a proper chamber to allow the bolt to close unless the cartridge wasn’t properly crimped in place.
    There appears to be another problem as the hammer shouldn’t drop if the bolt wasn’t closed.

    • You would think that. But 300 is based off the 223 case. Depending on the bullet and powder load, it can setback and chamber. Looking at the damage, it is obvious the bullet didn’t move too far down the 223 barrel. Instead it blew the upper apart.

      Freeze was telling me of a case where the 300blk actually went pretty far down a barrel but was squeezed and elongated to 22 caliber.


      • 1918A3BAR

        When I seen this picture I instantly thought someone grabbed the blackout round (probably a handload) stacked it in the magazine loaded the rifle and dropped the bolt home and probably didn’t have a crimp on it the case and it pushed the bullet into the case far enough for the bolt to go into battery and kaboom

  • Lincoln Pope

    So………the problem with the RIFLE is that it’s too easy to put the wrong ammo in it? Sounds to me that it’s a USER error. If you put regular gas in a diesel, who’s fault is that?

    • Fair point. As long as you factor in the cost, time, and logistics of the mistakes which statistically WILL happen.

      Just like the paramedics who put regular gas in their diesel ambulances.

      Every. Single. Year.


  • Bob Harris

    So, in other words, if you are a moron, you should avoid the 300BO. Otherwise, if you use some basic common sense, the caliber is perfectly OK. Gotcha.

    • Bob, the truth is humans are fallible. Nothing we do or say will eliminate that completely. All we can do is educate people so they can be aware of the potential pitfalls. This gives them the tools to help negotiate these pain points.

      I recall when this kind of stuff first came up and the consensus was, by people who it appears actually didn’t know the answer, this was mechanically impossible.

      Now at least the community is aware.


  • Scott Ladrochelle

    You wrote “But 300 Blackout doesn’t do anything for me that standard calibers don’t.” The 300 Blackout penetrates light to heavy cover and it is not as easily deflected. My experience during the war was that the 5.56 mm was easily deflected by light foliage and the enemy knew that, their AK rounds did not have that issue. Where I live there are creosote and mesquite among the tall grass and thistle, you can see though the foliage at spots but I can’t reliably hit a target behind that growth with a 42 round magazine of 5.56mm. I have no problems hitting the same target with either the .300 Blackout or the 7.62 X 39mm. We won’t even begin talk about stopping power or getting water in the bore.

    • Point 1:
      7.62×39 = the original 300 blackout.

      Point 2:
      You can achieve the performance you mention above, for the situation as you describe, with 7.62×51.

      Point 3:
      You can achieve that suppressed with subsonic 308 ammo.

      Point 4:
      You can buy a myriad of 308 rifles with 20-30 round mags if you need that many rounds suppressed. Again….not just that many rounds. That many rounds suppressed.

      Point 5:
      There is really only one thing 300blk does somewhat better than all the examples I give above. That is replace the HK MP-5SD with a AR pattern of rifle, for high-volume, EXTREMELY QUIET suppressed fire, at room clearing distances.

      Point 6:
      Of everyone of us who has cleared a room for real, it is a very, very, very, very, very, very, very, very, very, very small subset that needs to do that uber-suppressed, with high-volume fire, in order to not die.

      Now back to reality: this blog is for civilians. Who have to buy their own rifles and pay for their own ammunition and maybe…just maybe…pay for a little bit of training.

      If you can make the math work for you, carry on.

      If 300blk is the one thing that floats your boat and gets you pulling the trigger, carry on.

      If SOCOM is buying you pallets and pallets of 300blk, carry on.

      But logistically, the juice isn’t worth the squeeze in the non-SF, civilian world.


      • Scott Ladrochelle

        Oh absolutely, the .308 (7.62mm NATO) is a FAR superior cartridge! The 7.62 X 39mm AK a superior battle implement. My FAL does not suppress as successfully and the C308 (H&K Design) is a disaster at getting reliable performance when suppressed with subsonics. Their ergonomics make indoor use problematic. My .300 Blackout (and the .300 Whisper before it) has tons of users and builders with actual experience running subsonic suppressed in the compact M4 platform and their research and experience is golden! And the suppressed .300’s are very easy to deploy and their ease in switching from Subsonic to Supersonic is to be envied.
        Just remember in boot camp they issued us an M14 in 7.62mm NATO and we had to qualify at 500 and 800 yards. During the war they issued us the early M16, and maximum qualification range was dropped to 300 yards back then. I was NOT a fan and it’s shortcomings were deadly. If you are in love with the little guy, I am happy for you!
        I whole heartedly agree with your assessment recommending the 7.62mm X 39 AK’s and the 7.62mm NATO Battle rifles!
        In all the new AR’s are wonderfully Modular and calibers run the gamut from .22LR to .500 Beowulf.
        (.300’s need to be separated their magazines taped so identification (even in the dark) is easy and safety safety safety their new religion. Their reward is great though!
        And may you 22 bore guys not come under fire from light cover!)
        The government adopted the 5.56mm under the guise that it was better to wound an enemy, I felt somewhat better with a resounding stop.

        • That crack about 223 right at the end is where your logic consistently falls apart.

          300blk doesn’t make 223 bad.

          308 doesn’t make 223 bad.

          7.62×39 doesn’t make 223 bad.

          It’s not a zero sum game. I saw a video just yesterday where a full-sized 7.62x54R battle round didn’t get a one stop shot on a human with a frontal-face / head-shot.

          Shoot what you want. I just personally don’t have a need to dump 30 rounds fully suppressed, at room distances, into a human. Beyond that range, 300blk walks with the rest of pack performance wise for a short bit, then gets left behind.

          Some years I shoot more. Some I shoot less. Right now I am track for a typical round count year somewhere about 8000 rounds. 300blk doesn’t work for me performance or dollar wise.

          No worries.