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Thread: Reports of DD SBR barrels being over-gassed?

  1. #31
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    Quote Originally Posted by Apricotshot View Post
    I have a 12.5 DD and it is overgassed for sure. I'm using a H3 buffer right now. Felt recoil is greater than compared to my 10.5 and 16.5 middy.
    I can't imagine how DD could do this.
    "You people have too much time on your hands." - scottryan

  2. #32
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    Quote Originally Posted by markm View Post
    I can't imagine how DD could do this.
    It doesn't bother me. Just adding to the known instances. It's a beater upper anyway that I use for classes.

  3. #33
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    Quote Originally Posted by Apricotshot View Post
    It doesn't bother me. Just adding to the known instances. It's a beater upper anyway that I use for classes.
    Still... When I fixed my overgasser, it was a jaw dropping moment.

    And DD should friggin know better than that shit.
    "You people have too much time on your hands." - scottryan

  4. #34
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    Quote Originally Posted by BT6 View Post
    OP,

    I'm not sure as to where some of these gas port diameters are coming from but a DD 12.5" should be about 0.073. It is hard to pinpoint specific issues without first hand inspection and shooting it ourselves. If you need anything from us, give us a call and let me know. If you would like to speak to me, ask for Mozak and you'll get to my desk. Thanks for your business. We appreciate it.

    Matt @ DD
    Doing this now.

  5. #35
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    Did you measure the gas port? Or talk with a DD rep?

  6. #36
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    I had the same experience with a DD 11.5" barrel. I had to get an H3 in it and I still don't trust it 100% suppressed.
    "Not every thing on Earth requires an aftermarket upgrade." demigod/markm

  7. #37
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    Noodles do you have an update on your ""report" of the large gas port on your dd sbr?

  8. #38
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    Arrrgh, yet another mystery left unsolved. C'mon guys. Don't give us multiple "I'll check tomorrow" and then still mum two weeks later. This happens way too often where an OP poses a problem, gets suggestions and then solves problem, but never checks back in to share the resolution. Did Nell lube the the tracks or not?
    The beasts of modernism have mutated into the beasts of postmodernism—relativism into nihilism, amorality into immorality, irrationality into insanity, sexual deviancy into polymorphous perversity. And since then, generations of intelligent students under the guidance of their enlightened professors have looked into the abyss, have contemplated those beasts, and have said, “How interesting, how exciting.”

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  9. #39
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    Quote Originally Posted by uffdaphil View Post
    Arrrgh, yet another mystery left unsolved. C'mon guys. Don't give us multiple "I'll check tomorrow" and then still mum two weeks later. This happens way too often where an OP poses a problem, gets suggestions and then solves problem, but never checks back in to share the resolution. Did Nell lube the the tracks or not?
    Yea yea, thanks dick I have a real job that demands more of my time.

    Anyhow... DD has had the upper there for a week or so. I do have an update, but I'm starving so it'll have to be after lunch.

  10. #40
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    UPDATE:

    After posting my thread Matt @ DD reached out to me and we talked about a few things. He wanted to look at and examine that upper. So off it went and I just talked to him about it yesterday.

    The gas port on that barrel is exactly at .073 as it should be for their specs. That's good. HOWEVER... Matt did come back saying that for a 12.5" that upper MIGHT be a little bit more pushy than others. I'm starting to think the reason is the weight, the NSR is light, it just had an A2 on, no light, although the troy front sight was there. So, not sure.

    DD also decided to re-pin the block as the original job (done by DD) wasn't to their liking. They worked on that and cleaned it up for me. It's back in the mail and will be here next week.

    One note.... The port is .073. The DD Mk18 FOR SOCOM (unknown on Commercial Mk18) has a Crane* dictated port of .070 for the 10.3, meaning, with Nato ammo my gun should be able to run at least a .65-.68 port or so. But... This is the issue with all AR barrels... Do you want it to run NATO ammo only or the widest range of ammo possible? As a civ, am I always going to be able to get my paws on the good shit? DD is correct in upping the port for their commercial products. I would prefer this gun run always and forever with any ammo. So, the DD .073 port MAY be oversized for my needs on this specific gun - but it is not "overgassed". There is a magin there, and I'm sure it's on the safe side, but nothing I would consider "incorrect".

    * Note, the Crane Mk18 testing and MRBS (mean rounds between stoppages) is in my opinion pathetically low... like under 1k in all 5 test guns. That's full auto with 10% suppressed usage, but still. I would consider researching why that was if I were building a 10.x gun.

    So.... My issue..... I think it's a couple things I've worked out and their fixes.

    1. I'm putting a brake on it. For some reason when I think back to why it has a flash hider, I seem to recall reading a lot about how "SF brakes are too loud", and how ungodly it is to be to the side of them, etc. Well..... After spending three days shooting to the right of a guy using a 14" 762 AR-10 with a brake - YES they are loud, but nothing too loud. That 762 was annoying but manageable for sound and dust when on the ground. I probably wouldn't do a brake on that gun, sacrificing speed for power, but whatever. A 556 gun isn't half as bad (had one to my right). But the larger point here is **** YOU, I don't care about your hearing or comfort on the range or anywhere else. I care about putting rounds where they need to go as quickly as possible. As a civ, I also don't care about flash, if I do, I'll toss the can on. So... pretty much SF socom brakes from now on. DONE.

    2. That gun is light. It's 6.6 or so unloaded. I'm going to bulk it up a bit with a Fury in a keymod mount and with the can on it (any week now!) I'll reevaluate.

    3. I'm not 100% sure about the A5 buffer. I've been kicking around the difference between a fast cyclic rate with low reciprocating mass vs a low rpm with high mass. I'm sure the best solution is a balance or as stiff a spring and light a buffer as it'll run acceptably. So in that vein, Allen at Sprinco is sending me a Green A2 spring to experiment with. I'm fully expecting to wind up with a Green + A5H2.

    4. Robert at MicroMOA has sent me one of his adjustable gas blocks. I'm very interested in this. I have a few plates so I'll be able to dial it in exactly. The real gem here is that if my gun runs at .067 unsuppressed, I'll also have a .046 or so suppressed setting. This is the only true solution to running suppressed perfectly. I'm going to see if I can get this on highspeed at some point. I'll have to wait for my cans to get here (or run a thread on at my dealer). There is an chance I'll have to use the .070 or larger plate for unsuppressed, but maybe not.

    5. I had Steve Fisher at Magpul confirm that gun was recoiling a bit more than it needed to. However... It's still not exactly fair of me to expect that gun as was to keep up with a 8.5lb BCM EAG with a BCS comp on it. Then again, if my gear wasn't letting me do the things I wanted to do, time for different gear! Which is how I got here in the first place.

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