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Author Topic: Dissipator Reliability  (Read 5225 times)

Tom The Impaler

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Dissipator Reliability
« on: December 22, 2013, 06:14:46 pm »
I built my first AR15 project a year or so ago and made what I think was a bit of a newbie mistake. I made a Dissipator. That is I made a dissy from scratch using among other things a DTI barrel, long gas system, 16" barrel. Now it feeds 62 gr military loads just fine but 55 grain loads are great for practicing stovepipe / FTE drills. I was wondering if a low mass bolt carrier group would help or hurt the problem? or perhaps a muzzle device of some type? A simple YHM phantom comp didn't help I can tell you that, though it cuts perceived recoil somewhat. What say you oh great sages?
« Last Edit: December 22, 2013, 06:36:19 pm by Tom The Impaler »
Some people call the midwest the heartland, I prefer to think of it as the liver. Not too interesting, and easy to ignore until it quits working.

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    GeorgeHill

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    Re: Dissipator Reliability
    « Reply #1 on: December 22, 2013, 07:08:44 pm »
    A Dissy is a great configuration and I have always wanted one.  But as you have found out, you want a Mid-Length gas system.  A good gunsmith could fix it, but you for the time and money, really you might as well buy a new barrel.
    Or, you just keep what you got and stock up on the heavier ammo, because it's just fine. 
    Polish the bolt carrier and the carrier's raceways, lube it up with slipstream and it will work it's way in and get better.
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    Tom The Impaler

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    Re: Dissipator Reliability
    « Reply #2 on: December 22, 2013, 08:00:12 pm »
    I'm already working on my second upper, making a mid length setup as they're well regarded. Just wanted to know if there's a "bolt on" fix. I'd like to be able to run anything. The great ammo scare of '13 proved I can't depend on getting what I want so I want to make what I've got run a bit better even though I'm working up a more expensive fix. Besides I wanna make it work sort of as is. I saw these...

    http://www.cpwsa.com/JP%20bolts_and_carriers.htm

    and thought maybe a lighter bolt could help, but I know engineering's harder than that so I thought I'd ask those who know better. or perhaps a "pig" muzzle device to help keep chamber pressure up. Now you've got me thinking along friction reduction lines though I may try a bit of that.
    Some people call the midwest the heartland, I prefer to think of it as the liver. Not too interesting, and easy to ignore until it quits working.

    GeorgeHill

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    Re: Dissipator Reliability
    « Reply #3 on: December 22, 2013, 08:18:30 pm »
    I don't think a Pig would help much.  I could be wrong though.
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    mattitude

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    Re: Dissipator Reliability
    « Reply #4 on: December 22, 2013, 08:33:37 pm »
    That's a bit odd that 62gr loads cycle but 55gr loads don't...it sounds more like an issue with the build but you are wanting to put a band aid to mask the problem instead of fixing it.  I doubt a low mass BC is the answer.  I think you should go back and completely tear down your rifle and inspect every part and then put it back together.  Pay close attention to the gas port alignment with the block, gas key bolts, gas rings on the bolt and possibly even the gas tube itself for defects. 

    Your rifle should cycle pretty much any 5.56 milspec ammo you feed it...if it doesn't then more than likely something is assembled wrong or a part is defective.  It's hard to diagnose a problem without seeing it, but there are a few things that I listed for you to look at.  Good luck!!
    North CarolinaMedically retired Air Force (17 years, 7 months & 25 days)

    GeorgeHill

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    Re: Dissipator Reliability
    « Reply #5 on: December 22, 2013, 09:31:22 pm »
    Not that add.  When Bushmaster first brought out the Dissipater with a rifle length gas tube, it pretty much had the same issue from what I saw in my friends' Dissipators.  Which is why I never bought one.
    (And yes, they did get rifle length gas systems from Bushmaster)
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    only1asterisk

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    Re: Dissipator Reliability
    « Reply #6 on: December 23, 2013, 12:22:06 pm »
    The rifle length gas system doesn't have enough dwell time with a 16" barrel to be fully reliable.   Some ammo might work, some others may not.  Heavier  bullets have lower velocity and thus longer dwell times.

    Tom The Impaler

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    Re: Dissipator Reliability
    « Reply #7 on: December 23, 2013, 06:19:14 pm »
    Yeah, what George and Only1 said. I'm just trying to get a bit better use out of this upper before building my second, preferably without blowing the bankroll or making the thing look silly. I have heard for instance that the muzzle device on the Krinkov exists to help keep bore pressure and dwell time up to increase the reliability. Like I say the 62 grainers run like champs, at least they have for the first 500 or so rounds.

    The lightweight BCG above was a bad example, others cost much less. I want to keep this since it's sort of sentimental. It's the first gun I've built by myself from scratch using parts I selected. also I'd feel guilty selling it to someone as a semi functional part. I want it to work.
    « Last Edit: December 23, 2013, 06:36:58 pm by Tom The Impaler »
    Some people call the midwest the heartland, I prefer to think of it as the liver. Not too interesting, and easy to ignore until it quits working.

    Tom The Impaler

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    Re: Dissipator Reliability
    « Reply #8 on: December 23, 2013, 06:43:47 pm »
    Oh and I'm pretty confident of the gas block lineup. As others have said, this is a known issue with Dissy's. Polishing the carrier and raceways might be the cheapest and most effective route to try at first. A bit of polishing rouge in the raceways, fire 50 rounds and clean?
    Some people call the midwest the heartland, I prefer to think of it as the liver. Not too interesting, and easy to ignore until it quits working.

    mattitude

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    Re: Dissipator Reliability
    « Reply #9 on: December 23, 2013, 07:40:17 pm »
    I've not seen a Dissipator with a rifle length system so yes that would be a problem.  I've only seen them with carbine length systems with a "dummy" front sight gas block pinned like it was a rifle length system to accommodate the rifle handguards.  This is what I'm referring to:  http://commons.wikimedia.org/wiki/File:Dissipator_Barrel.JPG
    North CarolinaMedically retired Air Force (17 years, 7 months & 25 days)

    Tom The Impaler

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    Re: Dissipator Reliability
    « Reply #10 on: December 24, 2013, 08:48:15 am »
    Oh yeah, and if I were doing it over I'd do it that way for sure, but this is a relatively expensive fix. I may give up and do it anyway, I was just hoping for a screw on solution with less time/money/energy involved. In the end though this may be the best solution. Heck there's nothing cheap about the fixes I've been looking at after all really is there?
    Some people call the midwest the heartland, I prefer to think of it as the liver. Not too interesting, and easy to ignore until it quits working.

    Nick Cage

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    Re: Dissipator Reliability
    « Reply #11 on: December 25, 2013, 04:11:52 am »
    You can also ream out the hole in the barrel a LITTLE to get the system more gas.
    Don't want to over do it but I've seen a walk through somewhere on the net... can't put my fingers on it.

    only1asterisk

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    Re: Dissipator Reliability
    « Reply #12 on: December 25, 2013, 07:06:57 am »
    Oh yeah, and if I were doing it over I'd do it that way for sure, but this is a relatively expensive fix. I may give up and do it anyway, I was just hoping for a screw on solution with less time/money/energy involved. In the end though this may be the best solution. Heck there's nothing cheap about the fixes I've been looking at after all really is there?

    I wouldn't be looking at those fixes when Adco charges $35 to relocate a gas port.  Even if the have to cut a new seat, it would be $100 or less all in.  With a lopro gas block at the midlength position you'd be out $150 plus shipping.  Then you'd have it fixed right instead of putting a bandaid on it.

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