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The entire point of 300 AAC Blackout is that you don’t need to change any of your existing gear. The cartridge fits in existing AR-15 magazines, the barrels fit into existing AR-15 upper receivers, and the bolts are the same bolts you’d get with any 5.56 NATO rifle. But Magpul has gone ahead and made a version of their PMAG specifically for the 300 BLK cartridge. Here’s what they have to say about it.

The PMAG 30 AR 300 B GEN M3 is a purpose-designed magazine for rifles chambered in 300 Blackout. Since its inception, 300 Blackout shooters have had to use a magazine designed for another cartridge, limiting its performance and compatibility. One of the nice features of 300 Blackout is the compatibility with 5.56x45mm parts, but with the magazine it is a compromise to do so. Due to the wide variety of projectile weights and shapes potentially decreasing overall reliability, a dedicated 300 Blackout magazine was a logical step for the PMAG line.

In addition to the performance gained by a dedicated mag, the PMAG 30 AR 300 B also offers a safer way to feed your 300 BLK rifle. When using 5.56 mags, the potential to chamber and fire a 300 BLK round in a 5.56 rifle with catastrophic results requires diligent ammunition management by the shooter. The PMAG 30 AR 300 B’s distinct rib design provides the shooter a distinct visual and tactile difference from any other PMAG to mitigate dangerous cross-loading issues. Along with optimized 300 BLK performance, the PMAG 30 AR 300 B brings along all of the GEN M3 features such as our next-generation impact and crush resistant polymer, aggressive front and rear texture, an easily removable slim floor plate, a paint pen dot matrix for marking and identification, and a dust/impact cover.

  • Dedicated, purpose-designed magazine for rifles chambered in 300 Blackout

  • Optimized internal geometry accommodates the wide variety of bullet profiles used in 300 Blackout cartridge

  • Distinct rib design provides the shooter a visual & tactile difference from any other pmag to mitigate dangerous cross-loading

  • Carries forward the physical & performance features of the rest of the gen m3 line

MSRP is about $15.95.

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  1. At first I asked myself why, but then I released some of the longer subsonics might not be 100% in your 5.56 mags, so it makes sense. I’m not absolutely sure, but usually Magpul doesn’t make stuff that nobody needs/wants.

    The only thing left is reliable and cheap 5.45×39 mags.

    • I wonder if these mags would work with 80+ grain .223 bullets? Also, the 5.45×39 market is dying, unless Trump commands the ATF to allow more 7N6 in.

      • The 5.45 market is dying? Maybe it is maybe it isn’t. But Arsenal is putting out 5.45 AKs. Right now there is only a few choices. Either $45+ or not worth buying. I’m glad Magpul got into it. Wish they did years ago.

        • I would take that as a good signal, for two reasons:

          1. Arsenal AKs are not cheap, you are generally looking at $900 minimum for a used Arsenal SLR rifle.
          2. Arsenal discontinued their 5.56 SLR variant, so you can’t argue they’re doing it “just cause”

          I think these two facts together might lead one to the conclusion that there is clearly a market for 5.45 AK rifles still

        • There certainly is a market for 5.45 rifles, but it is no where near as big as it was back when you could get cheap surplus ammo. That was the 5.45’s largest draw.

    • I just pretty up some pmags that started sand colored. 10 minutes on the stove in a vat of something colorful and my 300 BLK ammo has its very own cribs.

      • Mine are spray painted yellow and have some rather entertaining floral pattern duck tape on them. Mistaking them would almost have to be deliberate.

      • It’s not just the external change though. The ribs inside are different to accommodate 230gr+ bullets that won’t feed from a normal Pmag. I’ve been painstakingly filing down the ribs in my old Pmags to do this. It will be great to buy mags that are ready to go.

  2. These are a good idea for a mag full of 220 grainers – way heavier than anything you could cram into a .223 / 5.56 case. The 20 round mags at work with tired springs can feed 20 rounds of 64 grain GDHP just fine, but can’t deal with 20 – 220 grain 300 BLK subsonic rounds. I download my fresh mags to avoid issues with heavy subsonics.

    Good on Magpul for their continued innovation, as well as their 2nd Amendment advocacy.

  3. FWIW
    I run supersonics through GI and magpulls all the time with no issues.
    Some people claim subsonics have issues and that Lancer mags feed them the best.
    I have a bunch of subsonics but I haven’t gotten around to trying them out.
    I agree that if you have a 300blk and a 5.56 you better be very darn sure which mags have 300blk

    • … Which is one reason I intend to never have those two calibers “in residence” at the same time. Bad enough with .40 S&W and .357 Sig.

    • It’s not just a claim. Depending on the subsonic bullet, some just will not fit into a 5.56 magazine because of the thickness of the bullet. The cast lead 220+ grain bullets are notorious for having magazine fitment issues in 300 BLK.

      • So I’m just trying to get this right is everybody using cast 250 + grain bullets to reload I’m not a Reload or so I’m asking I don’t really know that’s why I’m asking the question is there a reason why you don’t stick to a 220 grain bullet one that fits in the magazines and will run in the gun correctly I know cast bullets are a lot cheaper and you can manufacture them yourself but why not stick to something around two hundred grains something that will run in the gun without having to modify the magazine.?? What I guess I’m asking is what are the benefits of running a 250 grain 260 grain LED bullet vs. Using a copper jacketed 220 grain bullet? I guess that’s what I was trying to ask what are the benefits of using the higher grain bullet besides having a slower bullet?

        • subsonic is by definition velocity limited. Therefore to increase energy you have to increase projectile mass.

        • Yes to increase energy on impact you need both velocity and weight. You can shoot a 500 grain bullet going 600 feet per second and you’re not going to get the penetration that you get out of a 200 grain bullet go in a thousand feet per second or maybe 11:50 feet per second. It’s a balancing act between weight versus velocity.

  4. There are companies that we trust, and companies that we don’t. Magpul is one that we trust. If Magpul brought this product to market because standard 5.56 mags weren’t good enough, I’m inclined to believe ’em.

    • Meh. Maybe. I run 220 subs through 30-rd lancers without a problem.

      Perhaps this is more to address a weakness of the 5.56 Pmags in particular?

      • The PMags have a set of ribs on the inside of the mag that (I assume) facilitates the anti-tilt feature. These ribs rub against the side of larger subsonics causing odd stacking and possibly jamming depending on bullet geometry.

        The folks running coated cast bullets (some of which approach 250 grains) have had more pronounced issues with this. I’ve run into the issue with the Maker 200 grain subsonic.

        At the end of the day, Lancer mags are the way to go.

  5. My .02 worth – Magpul, like any other company, is not above a good marketing blitz, as the .300 continues to gain popularity.
    I readily agree to making the best distinction between the two calibers. And beefing up the mags to account for the heavier weight makes sense. But I see nothing about heavier springs which seemed most obvious.
    For me – I have two .300 and one 5.56. So my mags are all Lancer – black and smoke gray for the 300’s, and since my 5.56 is FDE clad, the mags are FDE and clear. Color coding works great!

    • Unless you’re shooting in the dark! Using 20-round mags for 300 blk and 30-round mags for 5.56…no mistaking what you’re feeding. Seeeemples.

  6. I’ve experienced a couple of PMAG M2 5.56 mags that won’t reliably feed in my 300 BLK with 110 gr. supersonic. Swapped to GI mags and eliminated the problem. We’ll see how these work.

  7. Most 30rd mags won’t feed my 247gr cast subsonics. This ought to be a nice addition for the rare occasion I need to load a full 30 of the quiet stuff…

  8. If I remember correctly the 300 AAC Blackout was designed to work with the 5.56 NATO magazines and receivers and bolt carrier groups why in the hell would I want a specialized magazine to put in my 300 Blackout rifles?? Sounds like another way to make a couple bucks off of some existing stuff by changing a couple of features on the magazine. I’ve never had a problem shooting my 300 Blackout with subsonic 220 grain bullets for supersonic 125 grain bullets and eat them up like fried chicken. Even with my M16 lower on my 300 black out it runs like a scalded dog I don’t know why Magpul would try to push something as if it needed its own style of magazine. The cartridge is exactly the same the only difference is where the shoulder meets the neck of the 5.56 it is cut shorter and opened up to hold the 7.62 millimeter bullet. Now if they’re talking about 220 grain subsonic ammunition and the chances of the weight of the bullets pushing the magazine follower down in the front that’s ridiculous. I have a 458 Socom and I shoot 350 grain bullets out of AR-15 magazines all the time without any feed problems. This seems like a scam. Just my opinion though.

      • Please help me to understand the relevance of your comment and I’m not trying to be rude by any means. I just don’t think there’s that many people out there loading 260 250 grain 300 Blackout. So if the demand to load a near 300 grain cast bullet is that great that you’re going to design a magazine and spend literally millions of dollars to launch a new magazine. It just doesn’t make sense to me no one that I’ve talked to that shoots Factory ammo has had any problem shooting the 220 grain or the hundred and twenty-five grain supersonic. And to be quite honest there are a lot of people that reload their own ammunition in America and across the world for that matter but how many of them are loading these high grain bullets to shoot every day out of their 300 Blackout not many. Seems like they’re just trying to create a fix for a problem that doesn’t really exist.

        • Lol they gave you a specific reason but you’re still claiming the problem doesn’t exist. Genius.

        • Well I do not reload so this is the first I’m hearing about cast bullets of 250 + grains or bigger causing magazine failures. Don’t know anyone that uses cast bullets anymore. All the guys that I come in contact with are using jacketed LED bullets. So I’m kind of in the dark about it because out of the 30 or 40 people I know that shoot 300 blackout on a regular basis they’ve had no problems with their magazines but then again they don’t shoot cast lead bullets that are 250 Plus Greens. I’m just trying to figure out why you would want to use such a heavy bullet made out of just LED.? So really if that is your issue just don’t use that type of bullet I mean it’s like any other gun some guns like certain ammo some guns don’t you don’t shoot but it doesn’t like. But I do have this one question what are the advantages besides cost of shooting a 250 grain lead bullet?? Maybe one of you guys can help me out with this?

  9. You also have to think whether or not you’re 300 Blackout rifle is using a pistol length gas tube or a carbine length gas tube. I’ve heard a lot of people having issues cycling lighter bullets with the carbine length gas tube. I’ve spoken with a couple of barrel builders that tell me the pistol length gas tube is the most appropriate for the 300 Blackout cartridge because of the powder it burns is pistol powder and it burns much quicker. That’s the reason why you can have a 10/2 inch barrel and burn all the powder up behind the bullet.

  10. I have a 556 gun and a 300BLK gun.

    I keep my magazines physically separated at all times.
    They are in their own boxes and in their own cases.

    But just to be sure I am not cross-loading magazines in the wrong gun
    in the dark
    I wrap a band of “Black” Electrical Tape around my “Blackout” Magazines.

    But I am considering of selling my Blackout gun and its ammo and going to
    an AK Platform.
    The cost of the Ammo.
    Blackout Ammo is over $1 per round in bulk.
    AK Ammo 7.62 x 39 is about .25 Cents.
    Go figure.

    • They already make them. I’ve never had problems finding them at Cabellas or most other stores around central Texas.

  11. My 5.56 mags are 30 rounders are black and have 5.56 painted on them (gray color sharpie). My 300 blackout are 20 rounders, are tan and have 300 blackout painted on them. No way to confuse them.

    • Yeah I can see where you’re coming from with the 165 grain Amax Hornady bullet. But to be honest I’ve had no failures except for maybe one or two ever since the 300 Blackout cartridge was released I have owned one. I’ve never had any failures shooting 220 grain jacketed hollow-point with a polymer tip. I’ve never had a failure with the cheap Walmart brand Remington UMC supersonic 125 grain hollow point. Now I haven’t kept magazines loaded with ammunition in them for the simple fact of the matter is it where’s your magazine Springs out. And when I load magazines I’d only put 28 or 29 rounds in a 30 round magazine never fully load to capacity I learned this in the military with GI magazines that causes flat feeds like a sumbitch. That’s with 556 NATO ammo though or the 300 Blackout if you leave the magazines fully loaded for long periods of time. But to be completely honest I just haven’t seen the failure rate there to make it seem reasonable to manufacture an entire line of magazines to shoot the round. Certain guns may not like certain brands of ammunition but I haven’t had that problem either I can shoot the cheap stuff or the higher-end expensive stuff with no problems. Besides were forgetting that the 300 AAC Blackout cartridge was designed to work with existing components of the M16 AR-15 rifle family why they use the 5.56 casing with some modification. My question is this really something that is really needed I mean is there that many people out there having that many failures with 300 Blackout that we need a magazine specifically designed for it?? I would have to say no with the experience I’ve had over the last few years and I served in combat so I know what it’s like to have a weapon system go down on you because of environmental conditions. But I just don’t see the need.

      • “Now I haven’t kept magazines loaded with ammunition in them for the simple fact of the matter is it where’s your magazine Springs out.” – This statement is untrue. Cycling of springs wears them out, not keeping them under continuous compression.

        • Constant compression will indeed wear out a spring, no matter what tempering process is used on the metal. It’s the same reason you never leave a torque wrench “set.” Next time you go to use it, it will be wrong, weaker.

  12. I’ve owned a 300AAC rifle for a couple years now and fired well over a thousand rounds ranging from 110gr up to 240gr. I’ve never had a single malfunction caused by a magazine when it be PMags gen 2 or 3, or GI mags. The only issue I’ve had is getting it too damn dirty to operate. That’s just a factor of using a suppressor and testing out different powders. It is definitely a reloader’s dream for range of options and component availability (I can make ’em $0.25-$0.35 / rd).

  13. i kind of thought this was mildly pointless until i read some comments about the higher weights of the bullets that could produce feeding problems for subs. for that case, this is a good idea.

  14. Is anyone playing with .277 Wolverine instead of .300 Blackout? Opinion?

    It seems like most of the appeal of .300 Blackout is for SBR and Suppressor crowd but if someone does not care about those two tax stamps but still wants the bigger bullet then .277 Wolverine is the way to go.

    • I would agree with you but the 277 Wolverine is a wildcat cartridge where the 300 AAC Blackout is Sammi approved. And you can buy 300 Blackout at any local Walmart not so with the 277.

      • 300 Blackout was a wildcat at one time too. .277 WLV is probably 1-2 years behind .300 Blackout in terms of popularity and production. If and when it gets Sammi approval then I’d say popularity will increase. .277 WLV is what 6.8 SPC should have been.

        • Here’s the issue does the 277 Wolverine cartridge fit into an existing 5.56 NATO bolt face or does the face of the bolt have to be opened up because with the 6.8 I have noticed bolts blowing apart because there’s just not enough metal there to support the face of the bolt surface and the rim of it. The 6.5 has some of the same issues with their bolts failing. The 300 Blackout cartridge is basically a 5.56 NATO cartridge that the neck has been cut short and expanded to hold the 7.62 millimeter bullet but the case and the size diameter is the same as the 5.56 on the backside of it so you still have it completely supported chamber and bolt face without having to remove metal from the bowl to make the cartridge fit into it.

        • There is no bolt adjustment with .277 WVL. The only thing that changes on the rifle is the barrel.

          6.8 SPC was based on the .30 Remington cartridge. Maybe it could be explained this way – You have AR15 and its wildcats, you have AR10 and its wildcats, 6.8 SPC tried to do its own thing.

          I don’t think any knowledgeable shooter would disparage .270 Remington so why not shoot .277 WLV?

          Another point is that if you are willing and able to reload your own ammo and would get in to .300 BLK then you would probably do .277 WVL. Its the same brass either way.

  15. I tried my new 300blk PMags in my 7.5″ SBR this weekend and the gun would not feed a new round. At first I thought I was having a gas issue (which this gun has never had). Checked all the usual suspects (BCG, tube, block, gas rings etc) all were good. So I switched back to my 5.56 PMags and the gun ran flawlessly. I’ll have to try them again later since I didn’t want to spend my whole range day screwing around with these mags. I was shooting 124gr which is what I usually run in it. I’m wondering if anyone else has seen this problem.

  16. If I were to mistakenly take these dedicated 300 BLK mags to the range with my 5.56 rifle, could I use them as a substitute for my 5.56 mags? Would there be any reliability issues feeding the 5.56 ammo?

  17. I simply use metal “GI” mags for 300BO and PMAGS for 5.56. easier to not get them confused and they run 245gr Subs with no issues.


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