300 AAC BLACKOUT – New caliber brings 7.62 punch to AR platform


Calibers come and go, but not usually from companies that are tied into military contracts.  With the M4 replacement testing coming up in the near future, we weren’t surprised when we got a call from AAC/ Remington telling us about a new project.  What we didn’t see coming was that sneak peaks would be done at Modern Day Marine.  Luckily, we were on hand as Marines in the know petted and panted over the pumped up SBR.

As interesting as a new caliber is to some of us, it gets better.  Start thinking about a M4 with a 9″ barrel that matches the energy of 5.56mm M855 from a 16″ barrel (the standard M4 is a 14.5″).  The 300 AAC BLACKOUT 123 grain ammunition matches the ballistics of the 7.62x39mm AK and has 37% more energy than 5.56mm M855 when either are fired through a short barrel.  Clearing buildings, crawl spaces, vehicle work, going up ladders and seizing ships or aircraft are all tasks that have us wanting a short barrel, but getting shot at has us wanting a round that ends threats quickly.  It looks like the new 300 AAC Blackout from Remington/ AAC ammunition and upper receiver is at the right place at the right time.

Click on the picture for loads more information, and of course, lots more pictures.


We spoke with Robert Silvers who is the Research and Development Director for Advanced Armament Corp.  Mr. Silvers explained that they had developed not only a caliber, but also an upper receiver group that would drop on existing M4 carbines (or AR15s).  This upper receiver group uses a standard  M4 bolt and Bolt Carrier Group (BCG).  We pointed out that this allowed for an immediate swap for Military or Law Enforcement teams that were already using the M4 as all they would need would be for their armorers to change out barrels.  I don’t think my observation was anything new, and he agreed.  He went on to state there were three types of SAAMI approved ammunition immediately available with additional options coming up in the near future.

Current ammunition types are the 123 gr. MC 300BLK, 155 gr. OTM 300BLK, and 220 gr. SUBSONIC OTM 300BLK.  Each round is purpose driven, and allows selection for a given mission.  The supersonic ammunition was developed as a 5.56 replacement, while the heavier subsonic ammo was designed to give a total weapon replacement option for users of the MP5 and MP7.  Barrier Blind Optimal Penetration ammo is currently under development.

One weapon and caliber replacing the standard M4, AND the more specialized HK MP-5 and HK MP-7A1?  It sounds like a congressman or city managers prayers have been answered, never mind unit armorer and supply guys.  Money issues aside, training with one weapon platform makes more sense than jumping back and forth.  Of course we use the best tools available for the job, but sometimes less is more.

Advanced Armament Corp is best known for their suppressors, and it makes sense that along with the development of the upper and ammunition, a silencer would be included.  The numbers given to us show the new 762-SDN-6 suppressor is shooting a 220 grain 300BLK bullet at 1000FPS at 126.2 dB.  The  MP5-SD is firing a 115 grain bullet at 900FPS at 130dB with its HK suppressor.  I understand that these numbers were not done at the same time, and that various testing methods can show different results, so I look at these as rough numbers.  Anyone who had fired a suppressed MP5 knows how quiet they are, so even as a ballpark figure, these numbers are impressive.

Below are the listed design objectives as they were given.  When I asked who had come to AAC/ Remington with these design objectives, I was met with a moment of silence, and told it just came as part of a project.  Fair enough.


• Create a reliable compact 30-cal solution for the AR platform
• Utilize existing inventory magazines while retaining their full capacity
• Create the optimal platform for sound and flash suppressed fire
• Create compatible supersonic ammo that matches 7.62×39 ballistics
• Provide the ability to penetrate barriers with high-mass projectiles
• Provide all capabilities in a lightweight, durable, low recoiling package

Mr. Silvers pointed out several times that this was not a caliber that was exclusive to the Military or Law Enforcement market.  His stated his goal was to be able to deliver a reliable source of ammunition through Remington, and to make the 300 AAC Blackout something affordable for target shooters and hunters.  There are a lot of AR15 shooters in this country, and a lot of hunters, but most states will not allow hunting with a .22 caliber.  The advent of the 300 AAC Blackout may bring interest from a few other avenues as news of this circulates throughout the shooting community.  While 6.8SPC is an option, there many people who will like the ability to use their current AR15 magazines, as well as using a standard 5.56 bolt.  Ammunition reloaders may find their .30 favorite bullets another reason to look at the 300 AAC Blackout.

There is a lot more information that we have on this weapon system, but we have one in hand, and ammunition enroute to us.  We are going to put the weapon and rounds in the hands of MIL and LE trigger pullers, then report back with our findings.  For now, check out the new website and start soaking it all up.



About Author

8 year USAF & Desert Storm Veteran, Current city Police Officer, Armorer, firearm and tactics instructor. Photographer specializing in weapon photography and weapon T&E.

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  1. “The 300 AAC BLACKOUT 123 grain ammunition matches the ballistics of the 7.62x39mm AK and has 37% more energy than 5.56mm M855 when either are fired through a short barrel.”

    With the increase in energy, I wonder what the long term effects on the life of the rifle’s barrel? It’s being widely reported that high energy calibers like the .338 Lapua really eat up rifle’s boring and as such significantly decrease the lifespan of a barrel.
    Still though, a very interesting development that may add another argument to keeping 5.56mm as the primary caliber for rifles & carbines in the US inventory for the interim until something truly revolutionary such as CTA rounds and weapon systems become fully developed.

  2. @Matt

    Barrel life should be even longer then the 5.56 since the hot gasses are going out a larger pipe. It’s going to have no where near the pressure and amount of hot gasses that a round like the .338 Lapua does.

  3. Matt-
    The increase in energy is from the increased bullet mass and not from increased velocity/powder charge. The 300BLK powder charge and velocity are both lower than 5.56, leading to longer barrel life than current systems.

  4. For me this is the first day of a new century in ammunition technology . Same Velocity (SPC) , smaller cartridge , less powder . I can not even start to imagine the cartridges that are going to be produced after this one . Also i would like to point out that by the progress that i am seeing the past few years in the ammo industry , believe that the CTA goals could be (at least) achieved by “curent” technology ammunition , without the billions spend in R&D , cheaper and quicker .

  5. I’ve searched for larger calibers for my AR builds and went as far as buying a bolt and magazine for 7.62×39. If the new Remington round matches ballistics of the 7.62×39, then why spend the money on Remington? I believe that more people would jump to the 6.8SPC if prices would come down. The ballistics are better than 7.62×39.

  6. The reason the 338 Lapua eats barrels is due to high velocity, and therefore high temps inside the barrel. The energy being talked about here is referring its performance on targets.

    As to the weapon/caliber itself, meh, I would rather just have a full power .308 (7.62×51) After fifty years we are coming full circle. We should have just advanced the design of the M14, and today Troops would be fielding weapons like the M1A Socom, and we wouldn’t have this “problem”. When they took the emphasis off marksmanship, and put it onto “Volume of fire” they created the problem we are now trying to fix.

  7. Due to the small powder volume that this case has as well as the larger bore diameter, it will have very good barrel life.
    Barrel life will far exceed the 7.62×51.

  8. As a former Marine I can testify to the utility of such a rifle. This looks like a 300 Whisper/300-221 that AAC just named different so they don’t have to pay royalties to J.D. Jones. What makes this a more attractive option, however, is that there isn’t any work the user needs to do to switch between subsonic and supersonic rounds. Most of the time with a custom 300-221 AR you still need an adjustable gas system to do that, which is a pain, unless you perfect your reloads. Kudos AAC, I love you guys! I’m just not happy that I won’t be the only guy I know with one of these for very much longer…

  9. Bill Siegloff on

    What is so new about this it is just a rebadged 300 Whisper.

    I am not impressed at all as e have had the same basic case and performance for years thanks to J D Jones of SSk industries.

  10. How is this different from the 300 whisper? Or also known as 300/221…

    Mine uses commercial .223 brass and 220 or 240 SMK’s….

    Subsonic barrel life should be infinite…mine uses 7.9gr of lil gun. Typical powder charge for is in the high twenties(gr)… The round retains energy like a mofo…

    These rounds are tough to make accurate at subsonic velocities(precision rifle use) but as far as sub-gun wouldn’t be too bad.

  11. This is basically a 300 Whisper / Fireball that has been around for a while. Wish they had just thrown support to the existing wildcat rather than create a new wildcat with the same ballistics and 1 or 2mm more case length. I just got a Whisper and do love 556 the bolt and mag compatibility.

  12. Stickman on

    The 300 Whisper never had support or SAAMI approval. AAC was very clear when I wrote this that this follows the 300 Whisper, they never tried to act like they were inventing magic, or something new when I spoke with them.

    By putting out a solid print and specs, then allowing any ammo company to make 300AAC BLACKOUT without paying royalties, they create a stable platform. It sounds like some 300 Whisper barrels will be able to use this caliber, I know that Noveske Rifleworks is getting the full prints to verify whether theirs will work or not.

    AAC commented that its hard to support a wildcat round when load data is all over, and loads for a TC are not going to be helpful for an AR.

    Hopefully this is of some help, I understand the 300 Whisper comments. The way that I look at it is that this is what the 300 Whisper could have been had things been done right from the start. Unfortunately doing things right in the commercial world means spending a ton of money. Remington and AAC can support this through their manufacturing capabilities and through their other resources.

  13. Stickman on

    Here is a quote from Robert Silvers, who is the project head on the 300 AAC BLACKOUT.

    “300 Whisper(R) can do the same thing. The problem is that I would say most load data for 300 Whisper is not very compatible with the AR15 for various reasons:

    1. OAL too long.
    2. Bullet won’t feed well in an AR.
    3. Powders inappropriate for the AR gas system.

    So much 300 Whisper load data is for Thompson Center and bolt guns only.

    So it was better to start fresh. While I cannot say it is compatible because it is certainly not with a military standard of reliability with all of the random old loads out there, it was not designed to be incompatible either.

    Remington 300 AAC BLACKOUT ammo is specifically designed to solve the reliability problems that people have had with 300 Whisper in the past. It was submitted to SAAMI and other ammo companies will be able to make ammo also, royalty-free. Likewise, many gun companies will be announcing 300 AAC BLACKOUT guns between now and the Shot Show.

    Reloading dies are available from Forster.”

  14. Here is a quote from Robert Silvers, who is the project head on the 300 AAC BLACKOUT talking about the 300 Whisper.

    “1. OAL too long.
    2. Bullet won’t feed well in an AR.
    3. Powders inappropriate for the AR gas system”

    What a load of manure. I have been shooting a AR in 300 Whisper for over 20 years now and none of the above comments are valid. The 300 Whisper fits fine in a standard AR magazine and feed perfectly as well, and I guarantee any powders that will work in this copy (300 AAC) would work just as well in the Whisper. Why not be honest and say you didn’t want to pay royalties so you made extremely minor changes that don’t affect performance and renamed someone else’s work? What does AAC stand for? Another Appropriated Clone.

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