HK416C Gas Problem
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Thread: HK416C Gas Problem

  1. #1
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    Default HK416C Gas Problem

    I am pretty familiar with HK416's and have operated different configurations and have had very few issues. I recently put together a HK416C with the correct C stock and bolt setup. Note the barrel, gas block and gas piston are from the 9" HKparts kit. I fired a couple of rounds through it and it jammed, the bolt would not move forward all the way into the chamber. Removing the hanguard revealed that the gas piston was pushed all the way back and it was stuck in the gas block. The gas rings were messed up not allowing the gas piston to slide back forward in to the gas piston. I pulled everything apart and replaced the gas rings with genuine German parts and tried it again, but had the same problem.

    I am thinking I have an overgassing issue. The gas block is marked 10". Any suggestions or anyone else have experience with this 9" kit?

    Thank you

  2. #2
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    Were you shooting it suppressed? I’ve heard of this happening on the HKParts/GSG9 8” and 9” barrel assemblies when fired suppressed. The only quick fix you can really do at this point is open the vent up slightly on the front of the gas block .1mm at a time and find the right balance to cycle the action or get in touch with GSG9.

    Need pics of your C build!

  3. #3
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    No, I should have mentioned that, I was not shooting it suppressed. This is the GSG9 9" setup.

    Thank you

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    Quote Originally Posted by blhar View Post
    No, I should have mentioned that, I was not shooting it suppressed. This is the GSG9 9" setup.

    Thank you
    There is a reason HK discontinued the model ...

    Just sayin’
    Brad4065 likes this.
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    This appears to be more of a manufacturing/tolerance issue.

    Without seeing the actual malfunction, and based on the description, possibilities include a too short of an op-rod/pusher rod or the op-rod spring is compressing too far and allowing the piston to fully unseat from the gas block which may allow the gas rings to expand further than normal under pressure while being free from the block.

    HK's are known for still being able to operate under duress for at least a short time unless another defect is added into the mix.

    As suggested above, reduce gas, double check which op-rod spring you are using and do your best to find out if it is compressing too much, double check length of op-rod and see if it is allowing the piston to fully exit the gas block.

    This could simply be a case of incorrect dimensions (gas vent) stacked tolerances (Rod length/gas block), incorrect parts(spring may not be long enough), or just crappy manufacture(all of the above)

    Just out of curiosity, when the casings ejected, where did they go and how far did they go?

    What length of op-rod spring

  7. #6
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    Quote Originally Posted by blhar View Post
    I am pretty familiar with HK416's and have operated different configurations and have had very few issues. I recently put together a HK416C with the correct C stock and bolt setup. Note the barrel, gas block and gas piston are from the 9" HKparts kit. I fired a couple of rounds through it and it jammed, the bolt would not move forward all the way into the chamber. Removing the hanguard revealed that the gas piston was pushed all the way back and it was stuck in the gas block. The gas rings were messed up not allowing the gas piston to slide back forward in to the gas piston. I pulled everything apart and replaced the gas rings with genuine German parts and tried it again, but had the same problem.

    I am thinking I have an overgassing issue. The gas block is marked 10". Any suggestions or anyone else have experience with this 9" kit?

    Thank you
    Will it function with a HK 416/MR556 lower
    it might help to try one thing at a time

    I built a 9" barrel with a 1.25mm gas port and a 10" gasblock with a 1mm vent and it seems to work well with a my stock MR-556 lower
    HK416C Gas Problem-9.0-pdw-2.jpg
    HK416C Gas Problem-9.0-pdw.jpg
    HK416C Gas Problem-9.0-pdw-3.jpg

  8. #7
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    Thanks for the replies. I did take a measurement from the back edge of the gas piston to the tip of the operating rod when you pull it back as far as it will go. On the C setup there is .15" more gap between the back edge of the gas piston and the end of the rod than the standard 10.4" setup. I was planning to test it with a German gas piston, also not sure yet on the operating rod spring tension as compared to the standard. I could always cut down a German op rod to fit the C.

    Does anyone have specs on a German HK416C operating rod?

    Thanks

  9. #8
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    Quote Originally Posted by blhar View Post
    Thanks for the replies. I did take a measurement from the back edge of the gas piston to the tip of the operating rod when you pull it back as far as it will go. On the C setup there is .15" more gap between the back edge of the gas piston and the end of the rod than the standard 10.4" setup. I was planning to test it with a German gas piston, also not sure yet on the operating rod spring tension as compared to the standard. I could always cut down a German op rod to fit the C.

    Does anyone have specs on a German HK416C operating rod?

    Thanks
    I have one at the shop I can give you the dimensions when I get home in a few hours

  10. #9
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    the 416C op rod is 32mm shorter than the standard one
    everything else appears to be the same
    HK416C Gas Problem-dscn8787.jpg
    Last edited by nefariousarms; 10-09-2019 at 12:11 AM.
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  11. #10
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    Thanks for the replies. I was able to get it to run. I changed out the operating rod spring to a German one. The spring that was on there was US made and a totally different compression rate and length. I still would like to find a genuine German HK416C operating rod sometime though.

    Thank you

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