HK 416 14.5 and 16" barrel gas port sizes - Page 2
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Thread: HK 416 14.5 and 16" barrel gas port sizes

  1. #11
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    veritas's Avatar
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    Quote Originally Posted by dms16 View Post
    @veritas ,

    Have you emailed Nefarious about this? Marvin and Beth may take a day or 2 but they've always been reachable and easy to work with.



    Blind diagnosis is that you're probably running just under the margin of operability/cycling and the can added is giving it enough back-pressure to help it cycle.

    No idea what the nature of PPU ammo but cheap Euro stuff generally runs 9mm hot and .223 cold. Could be the ammo...could be some unintended gas leak/bleed...could be a technical problem with the gas block, port dimensions, etc. Just as likely it may be multiple issues stacking together.

    I'd be curious about ejection pattern when suppressed as well as if you can hold the gun out like a pistol (the rifle equivalent of limp-wristing) and have it cycle suppressed. I'd also be curious to know what a full-blooded M855 or M193 would do in place of the PPU.

    Reducing the buffer weight (assuming you're following OEM buffer/spring) would be my last resort. More often than not it's manipulation is a bandaid attempting to fix other problems in the DI world when guys don't know what they're doing. Far better to find/fix the problem than catering to it.
    Thank you, I appreciate it! Yes, I have reached out to Marvin and will send him my complete upper to trouble-shoot it and possibly increase the port size. I cannot speak to the PPU ammo (M193 spec, so they claim) other than I have used it for years and had no issues with it; it seems to have a good reputation. I do wonder about the gas block and if there is an issue there, but I don't have the skills/tools to assess that. I guess putting on a vented, non-adjustable block and trying that might be a path to determining if it is a gas block problem. I did also recheck the rings on the piston and they are appropriately staggered so no leaks there. I did not measure the ejection patterns, but now wish I had.

    I agree on the buffer / spring as a "last resort" -- I want to address the source of the problem and not compromise somewhere else.
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  2. #12
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    RegularGuy461969's Avatar
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    I’m thinking it’s a 14.5”-16” Norwegian AGB; would be interesting to see what gauges say about the vent sizes on the regulator.

    Quote Originally Posted by veritas View Post
    Thank you, I appreciate it! Yes, I have reached out to Marvin and will send him my complete upper to trouble-shoot it and possibly increase the port size. I cannot speak to the PPU ammo (M193 spec, so they claim) other than I have used it for years and had no issues with it; it seems to have a good reputation. I do wonder about the gas block and if there is an issue there, but I don't have the skills/tools to assess that. I guess putting on a vented, non-adjustable block and trying that might be a path to determining if it is a gas block problem. I did also recheck the rings on the piston and they are appropriately staggered so no leaks there. I did not measure the ejection patterns, but now wish I had.

    I agree on the buffer / spring as a "last resort" -- I want to address the source of the problem and not compromise somewhere else.
    "Just because you're paranoid doesn’t mean they're not after you!"

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