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Thread: BRT 16" OPTIMUM Barrel w/ Extended Length Gas System

  1. #91
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    A 16" middy with an .076" port and an A5H2 buffer should run .223 like a top.

    A little more troubleshooting is required to narrow down the unusual ejection.

    Which BCG?

    Have you swapped BCGs or extractors?
    Last edited by Clint; 11-18-16 at 19:14.
    Black River Tactical
    BRT OPTIMUM HFCL Barrels - Hammer Forged Chrome Lined 11.5", 12.5", 14.5"
    BRT OPTIMUM Barrels - 16" MPR, 14.5" MPC, 12.5" MRC, 11.5" CQB, 9" PDW
    BRT EZTUNE Preset Gas Tubes - CAR and MID
    BRT Covert Comps 7.62, 5.56, 6X, 9mm
    BRT MarkBlue Gas Tubes - BRT EXT, EXC and PDW Lengths
    BRT MicroPin Gas Blocks - .750" & .625"
    BRT MicroTUNE Adjustable Gas Blocks
    BRT CustomTUNE Gas Ports

  2. #92
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    This, and ejector tension and drag on the ejector. Try Lutz's ejector lubing method and see if the ejector "feels" smooth or if there is some drag. Unfortunately, there's some components out there that are less than ideal.

  3. #93
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    Quote Originally Posted by Clint View Post
    A 16" middy with an .076" port and an A5H2 buffer should run .223 like a top.

    A little more troubleshooting is required to narrow down the unusual ejection.



    Which BCG?

    Have you swapped BCGs or extractors?
    The rifle started as a DD V7 so it's a DD bolt with Sprinco extractor and ejector springs. I'm actually starting to wonder based on your response. I'm starting to wonder shooting position. I laid a piece of plywood down in a field and used those idiotic Caldwell AR bags. It puts the lowest part of the mag 3.5 in off the deck. Lying prone behind that sucked...it was uncomfortable as hell. Maybe the awkward shooting position caused me to not be fully on/behind the gun?

    Bolt has maybe 2000 rounds on it...springs about half that.

    ETA..I pulled the bolt apart and all looks well. Plenty of tension in the extractor and ejector springs. Pulled extractor off and looks fine with no shavings in the channel.

    Eta to the eta...after thinking about my position I really had no way to provide enough abutment to not "limp shoulder" the gun. Left hand holding the rear bag and because of the design of the rear bag it interfered with my shooting hand grip...has to be it.
    Last edited by Glockman1968; 11-18-16 at 20:58. Reason: spelling is fundemental

  4. #94
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    Quote Originally Posted by Clint View Post
    A 16" middy with an .076" port and an A5H2 buffer should run .223 like a top.

    A little more troubleshooting is required to narrow down the unusual ejection.

    Which BCG?

    Have you swapped BCGs or extractors?
    It would run overgassed as shit. My Daniel Defense requires an A5H4 and is a 16.1" middy with a pin-gauged 0.074 gas port. Yeah, it runs wolf 55gr unsuppressed like a top, but anything more and it really is overgassed. Throw a can on it and suck-city. The 0.076 spec is even a bit large for a 14.5" middy. Daniel Defense ports their 14.5" middy (verified by pin gauge by me) at 0.076, and that's so it can ingest all sorts of cheap junk. Throw a can and some decent .223 or 5.56 at it, and overgassed a bit again...

    If I am building a 14.5" middy, it's going to have a 0.073 or 0.074 port, a 16.1" middy is going to have a 0.071-0.072 port.

    Just what runs great for me. YMMV, and there are other factors at play, I'm sure.

    Glockman, take that gas block, and tune it to 0.073 if you're running unsuppressed. Run an A5H2 and a Sprinco Green. Let me know how you like it.
    Last edited by WS6; 11-19-16 at 19:12.

  5. #95
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    In the interest of not taking this any further in Clints new barrel debut, Im jumping out of this thread permanently. I appreciate the feedback gentlemen.

  6. #96
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    Tight bore barrels will produce more gas drive for a given gas port size.

    This seems to be common with hammer forged barrels, but is not an exclusive trait to that process.

    Button rifled barrels can easily be produced with a similar tight bore using a custom buttons.


    A tight bore barrel will generally need one size smaller gas port to run the same as a "standard" bore.

    This needs to be factored in when comparing gas port sizes and inferring the level of gas drive a given barrel will produce.

    If further testing reveals this to be the case, a smaller .073" port can be easily swapped into the Micro Tune Gas Block to compensate for it.
    Last edited by Clint; 11-20-16 at 19:12.
    Black River Tactical
    BRT OPTIMUM HFCL Barrels - Hammer Forged Chrome Lined 11.5", 12.5", 14.5"
    BRT OPTIMUM Barrels - 16" MPR, 14.5" MPC, 12.5" MRC, 11.5" CQB, 9" PDW
    BRT EZTUNE Preset Gas Tubes - CAR and MID
    BRT Covert Comps 7.62, 5.56, 6X, 9mm
    BRT MarkBlue Gas Tubes - BRT EXT, EXC and PDW Lengths
    BRT MicroPin Gas Blocks - .750" & .625"
    BRT MicroTUNE Adjustable Gas Blocks
    BRT CustomTUNE Gas Ports

  7. #97
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    I agree that non conventional bore sizes, throat, and rifling, etc can change the pressure that the port is presented with, but .076" is large for a normal mid length gas 5.56 16" AR.

  8. #98
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    Quote Originally Posted by Clint View Post
    Tight bore barrels will produce more gas drive for a given gas port size.

    This seems to be common with hammer forged barrels, but is not an exclusive trait to that process.

    Button rifled barrels can easily be produced with a similar tight bore using a custom buttons.


    A tight bore barrel will generally need one size smaller gas port to run the same as a "standard" bore.

    This needs to be factored in when comparing gas port sizes and inferring the level of gas drive a given barrel will produce.

    If further testing reveals this to be the case, a smaller .073" port can be easily swapped into the Micro Tune Gas Block to compensate for it.
    And DD uses taper bore mandrels. So this further heightens that effect.
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

    "The body cannot go where the mind has not already been."

  9. #99
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    Quote Originally Posted by BufordTJustice View Post
    And DD uses taper bore mandrels. So this further heightens that effect.
    My dd bore is notably looser than my fn when dropping a geissele alignment rod down it.

    My question is also...will the port erode,or will the bore enlarge, first/more functionally significantly?

    Further, I am unaware of anyone anywhere using a tapered bore mandrel. It's not physically possible to get a taper that way due to how the barrels are fed over the mandrel. The tapering process occurs during other phases of barrel making.
    Last edited by WS6; 11-21-16 at 02:21.

  10. #100
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    Quote Originally Posted by WS6 View Post
    My dd bore is notably looser than my fn when dropping a geissele alignment rod down it.

    My question is also...will the port erode,or will the bore enlarge, first/more functionally significantly?

    Further, I am unaware of anyone anywhere using a tapered bore mandrel. It's not physically possible to get a taper that way due to how the barrels are fed over the mandrel. The tapering process occurs during other phases of barrel making.
    I seem to recall reading that some of the FN hammer forged barrels had some taper to them. I would assume that the port would start to erode before the bore would get worn away.

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