300 Blackout AR-15 Upper

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  • ironpony

    Member
    MDS Supporter
    Jun 8, 2013
    7,190
    Davidsonville
    Necessity pffffft. I just like to build, currently working on a .17HMR for the AR platform. Lehigh Defense is producing a 200 gr. projectile.



    Sarcasm. However I learned the most building and reloading for the 300. Like cutting a 556 cartridge down with a 12” chop saw can be done.
     

    RedTide

    The Water's Fine
    Jul 30, 2013
    177
    Frederick, MD
    However I learned the most building and reloading for the 300. Like cutting a 556 cartridge down with a 12” chop saw can be done.

    +1 :thumbsup:

    Still far from an expert, building 5.56 was nice to learn the basics of assembling a rifle (what feed ramps/gas tube staking should look like, pros and cons of different barrel steel, etc.). But building .300 blk was a bit different, as it takes a more complete understanding of the rifle to diagnose when something doesn't function (and it's much more likely that something won't function when you start drastically changing operating pressures).

    Reloading is a different beast, but I am glad to be dipping my toes there too. It's cheaper per round, but so much more...it's a wonderful curse of chasing perfection in ammunition.
     

    dreadpirate

    Ultimate Member
    Mar 7, 2010
    5,521
    Cuba on the Chesapeake
    Are you sure it doesn’t need to be heavy barrel?

    I’m looking at a complete BCM 300 Blackout upper for about $950 delivered. I’m just wondering if 300 Blackout is needed when I have 5.56 and .308 ARs. I’d match it to one of my Daniel Defense lowers.

    Sorry for the hijack.

    BCM uppers are nice; I got a 20" gov profile A2 upper for a pre-ban receiver and it shoots very, very well.
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    300 is an awesome caliber, a true intermediate round that has surprisingly similar form and ballistics to the original STG-44's 7.92x33 kurz. I always thought it was just an expensive and weaker alternative to 7.62x39 that would work with a standard bolt face and standard mag, but that isn't what makes it so good. It's a round that has a gigantic performance envelope, reminds me of 38 and 357mag, can be soft and quiet with mild recoil like a PCC, but with better ballistics than other pistol calibers, especially at longer ranges, and is DI instead of blowback with it's inherent limitations. At the top end it can push 30cal bullets to 1400FPE levels, plenty of power with bullet weights above anything that would fit in a .223 case. It really shines in short barrels, powders and pressure curves are more like magnum pistol calibers than a high velocity rifle, muzzle blast is nothing compared to 5.56 in short barrels, and it's reliable. Only real downside is the cost IMO, and that you will probably end up buying a suppressor to run it as it was intended.
     

    dreadpirate

    Ultimate Member
    Mar 7, 2010
    5,521
    Cuba on the Chesapeake
    Only real downside is the cost IMO, and that you will probably end up buying a suppressor to run it as it was intended.

    So 300 black is a potential money pit; ammo is expensive so you buy reloading equipment; works in a short barrel so you get a pistol, then pay to SBR, get a trust, get it engraved, then decide it would be perfect if suppressed. Need a new muzzle device to match the can. Then you need to get an adjustable gas block so super and subsonic operate reliably suppressed, etc.

    What's wrong with that? :D
     

    Major03

    Ultimate Member
    So 300 black is a potential money pit; ammo is expensive so you buy reloading equipment; works in a short barrel so you get a pistol, then pay to SBR, get a trust, get it engraved, then decide it would be perfect if suppressed. Need a new muzzle device to match the can. Then you need to get an adjustable gas block so super and subsonic operate reliably suppressed, etc.

    What's wrong with that? :D

    Hah! There is truth here.

    Actually ammo costs have come down quite a bit as the popularity of the round has increased. It's not so bad now if you don't reload.

    Like most things, you have to measure the performance of the 300 against the niche / need it is filling. It can be perhaps the best choice, or a really horrible choice depending on what you're looking to accomplish.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    I am of the "build it" club. If you go that route, build it as a pistol. You will be best served, if you choose to build/buy a pistol upper, to put it atop a dedicated lower. You will need an action spring made for 300Bk for more reliable performance. While you're at it, throw on an adjustable gas block(SLR). 10.5" or 8.5" barrel. That's where this platform shines. Eventually, you may get the itch to suppress it. Do as I recommended and the gun will be ready to accept a can without any other alterations.

    My 2 cents.

    Also, building it as a pistol negates the necessity or worry of a heavy barrel. They are not required on pistols or SBRs.
     

    DaemonAssassin

    Why should we Free BSD?
    Jun 14, 2012
    23,970
    Political refugee in WV
    I am of the "build it" club. If you go that route, build it as a pistol. You will be best served, if you choose to build/buy a pistol upper, to put it atop a dedicated lower. You will need an action spring made for 300Bk for more reliable performance. While you're at it, throw on an adjustable gas block(SLR). 10.5" or 8.5" barrel. That's where this platform shines. Eventually, you may get the itch to suppress it. Do as I recommended and the gun will be ready to accept a can without any other alterations.

    My 2 cents.

    Also, building it as a pistol negates the necessity or worry of a heavy barrel. They are not required on pistols or SBRs.

    I'm going 10.5" for a 300BLK pistol upper. I was looking at Rainier UltraMatch, but they don't treat the barrels from what I have seen. SLR adjustable block has always been part of my master plan.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    I'm going 10.5" for a 300BLK pistol upper. I was looking at Rainier UltraMatch, but they don't treat the barrels from what I have seen. SLR adjustable block has always been part of my master plan.
    I have that barrel on mine. You know what it's capable of.

    Sent from my SM-G965U using Tapatalk
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    Yes. Yes, I do. Hence the reason I want to use one, but I'd like it in basic black, sans pearls. I don't like silver barrels on a hunting rifle or HD pistol...
    See any pearls here?
    e220228a53754866fcbaa13705af2261.jpg


    Sent from my SM-G965U using Tapatalk
     

    DaemonAssassin

    Why should we Free BSD?
    Jun 14, 2012
    23,970
    Political refugee in WV
    Go satin.

    Sent from my SM-G965U using Tapatalk

    That is highly likely. I'm also serously condiering a Rainier Match or UltraMatch for a 16" build for when I start going after hearing safe options. I did some more digging and talked to some people, and I will be following the path you have with YHM. Probably be the LTA, if that is all they have on hand at the time.

    EDIT:
    Only real issue I see is the .800 GB seat. Cant find a SLR with .800 seat.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,815
    That is highly likely. I'm also serously condiering a Rainier Match or UltraMatch for a 16" build for when I start going after hearing safe options. I did some more digging and talked to some people, and I will be following the path you have with YHM. Probably be the LTA, if that is all they have on hand at the time.

    EDIT:
    Only real issue I see is the .800 GB seat. Cant find a SLR with .800 seat.
    I know. Kinda sucks they went that route. They do have .75 s but not in ultramatch anymore. That just means you can't throw an old .75 GB on it. SLR makes .80s.

    Sent from my SM-G965U using Tapatalk
     

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