Need 300BLK SBR build suggestions.

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  • rcm192

    Sic semper tyrannis
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    Alright guys...I'm building a 300BLK upper for my SBR. I currently have a Rainier upper and Ballistic Advantage 9" barrel with 1/7 twist. I have my Octane45 that I will direct thread and it will hold me over until my Omega is approved. When the Omega is approved I will connect via the ASR mount so the can will NOT be tucked under the rail.

    ...Oh and by the way I am running a PDW stock by NEA. Kind of a unique set up. The BCG has the buffer integrated into it. I am also using a tubbs precision flat buffer spring that has been custom trimmed to cycle with my current 5.56 dpms 7.5" upper.

    I have a few questions:

    -I am looking for a MLOK rail that will cut off as close as possible to the threads but still allow me to disconnect the ASR mount. SLR Rifle Works FAQs videos leads me to believe that 8.5" is my golden number for OAL of the rail. Who else makes a MLOK 8.5" rail?

    -Is an AR gas vent a necessity for 300BLK in general? Subsonic or supersonic?
    https://www.rainierarms.com/ar-gas-vent

    -Do I need an adjustable gas block? If so I think I want one with click style settings (unsuppressed, suppressed, single shot/off) unless you can prove to me that I need any other type that is offered. So...do I need one for reliability or what?! Lol. Who makes em?
     
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    Bigchillin83

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    I was kinda in the same boat for a 10.5" 7.62x39 pistol, also waiting on stamp for it. I ended up going with the 9.5" MI m-lok with the asr on my omega30 is about 1" from the end of my rail, yes I would have rathered one that almost flush, but that's how I did mine... that's about all I can add to this topic lol
     

    Saw

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    Me: 300blk 8.5" barrel with omega/ASR, standard carbine spring and buffer, no adjustable gas. Works great in all configs.

    Can't help with rail. As far as adjustable gas, you probably won't know until you try. The 300Blk by all accounts has a sweet spot that you can probably "set and forget" with an adjustable gas block. Another option you may have is tuning your integrated buffer with a combo of tungsten/steel to get it to run. Heavier buffers generally run great in 5.56 SBR configs too. Food for thought.

    I don't have a vent on my SBR lower and don't have any gas in the face issues. I do have a cheap knock off gas buster type charging handle (strike industries)that may help my cause. Haven't tried anything else.
     

    SpeedRacer

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    I really like the SLR rails (particularly the Solo Lite and Ion Lite) and they definitely have the most lengths to choose from. I just ordered an Ion Lite for my 8.3" 300BLK build.

    I just did lots of research on the same, and everything I'm reading says on a 9" BA barrel you shouldn't need an adjustable block or vent. Their gas ports are supposed to pretty well tuned as is, and it's even less of an issue if running supressed. A switchblock won't likely improve reliability, although it could make it shoot a little a softer with supersonic ammo. Juice probably isn't worth the squeeze on that though.

    Bottom line though is every build is different, so there's no way to really tell what you "need" at this point. When I'm building from scratch, I like to start simple and go from there. Standard gas block, standard spring and H1 buffer (or A5 if I'm feeling spendy). Then I shoot and determine where the system could benefit from being tuned. If it's overgassed, I fix it at the gasblock. Get that dialed in, then mess with buffers and see if there's any room for reliable improvement.


    Sent from my iPhone using Tapatalk
     

    noob

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    I have 2 300blk rifles, and my 9 inch sports a KAC URX4. fits nicely with my suppressor. I know it's not M-lock but it works for me, feels good. My 8.2 noveske runs a NSR rail. Both butt up pretty close.

    image_zpsi9fu6ljo.jpeg


    Here's the AAC upper which had it's URX 3 changed out for a URX 4

    image_zpsgdhdwgrt.jpeg


    And the 8.2 noveske that runs a NSR that's pretty close. Don't know the exact length since it came this way.
     
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    JoeLiberty

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    Why do the asr on that? Keep short rifle short with direct thread. How much are you really gonna shoot without the can?
    I run an 8" ballistic advantage and it's nice. Jp adjustable gas. While suppressed, the difference in the required gas for supers vs subs was not insignificant... But even open enough to run the subs reliably, the gas to the face is not bad woth supers. (I honestly don't have a lot to compare it to, and I could feel it but ot was not uncomfortable by any means). I'd say that adjutable gas is smart, especially since you can tune to whatever spring buffer setup and then you dont have to f with that swapping uppers. Hope that helps. Btw, do yall have any flat 30cal endcaps for the omega? Need dis.
     

    noob

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    I don't run adjustable gas on either of my blk guns (and had one with adjustable gas, that I never ever adjusted). Ran just fine suppressed and unsuppressed with subs and supers.
     

    Bigchillin83

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    i use the asr because i swap my omega out to all of my ar's and much faster and easier, pulse i have some dedicated to hunting with flash suppressors for if i decide not to use a can i wont have a muzzle blast and some dedicated personal defense/fun with muzzle brakes when i will be wearing hearing protection or not worried about hearing loss in a given situation.. no i still got the brake cap, i know dale at landry guns has some and cant beat his price, he was cheaper than internet on any extras i needed for my suppressors
     

    JoeLiberty

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    i use the asr because i swap my omega out to all of my ar's and much faster and easier, pulse i have some dedicated to hunting with flash suppressors for if i decide not to use a can i wont have a muzzle blast and some dedicated personal defense/fun with muzzle brakes when i will be wearing hearing protection or not worried about hearing loss in a given situation.. no i still got the brake cap, i know dale at landry guns has some and cant beat his price, he was cheaper than internet on any extras i needed for my suppressors
    He didnt when I picked mine up. :(
    I was hopin rcm had them for sale.
     

    Jmfox3

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    I just finished a pistol length gas piston upper. An adjustable gas block is strongly recommended. It will allow you some flexibility if you want to switch between sub and super. I do have a pistol length Adams Arms adjustable direct impingement gas block if you interested. Bought the Adams Arms but then changed direction to piston so it was never used. PM me if you're interested.
     
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    rcm192

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    Why do the asr on that? Keep short rifle short with direct thread. How much are you really gonna shoot without the can?
    I run an 8" ballistic advantage and it's nice. Jp adjustable gas. While suppressed, the difference in the required gas for supers vs subs was not insignificant... But even open enough to run the subs reliably, the gas to the face is not bad woth supers. (I honestly don't have a lot to compare it to, and I could feel it but ot was not uncomfortable by any means). I'd say that adjutable gas is smart, especially since you can tune to whatever spring buffer setup and then you dont have to f with that swapping uppers. Hope that helps. Btw, do yall have any flat 30cal endcaps for the omega? Need dis.

    i use the asr because i swap my omega out to all of my ar's and much faster and easier, pulse i have some dedicated to hunting with flash suppressors for if i decide not to use a can i wont have a muzzle blast and some dedicated personal defense/fun with muzzle brakes when i will be wearing hearing protection or not worried about hearing loss in a given situation.. no i still got the brake cap, i know dale at landry guns has some and cant beat his price, he was cheaper than internet on any extras i needed for my suppressors

    This is why I will use the ASR.
     

    JoeLiberty

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    Roger that. Another thought... If you want the handguard to end near the muzzle, the gas block is under there and harder to adjust (if you decide you want to tune the gas). I have had good success with an adjustable gas key from rubber ciy armory. Easy to tune, then u lock it in and leave it.
     

    noob

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    Depending on the rail you choose, the gaps/slots may be large enough for you to adjust a micro moa gas block using a pin/punch
     

    Bmash

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    On the subject of adjustable gas block, my SBR and 16" work fine suppressed and not with subs and supersonic without an adjustable gas block. (I handload and use different loads for subsonic to keep it around 1000fps and have to use different powders to ensure it would cycle without suppression.) I did put a Gemtech "suppressed bolt carrier" in my SBR. It was really tough on the brass when supersonic. So far works as advertised.
     
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