Hammer Spring Identification and Change (Non-Pinned Type)
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Thread: Hammer Spring Identification and Change (Non-Pinned Type)

  1. #1
    Unrepentant HKHolic
    retrodog's Avatar
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    Default Hammer Spring Identification and Change (Non-Pinned Type)

    This has come up here (and other places) so it's about time that we started documenting some of this information, so I took some measurements and a photo.

    The information and instructions were inspired by all the HK94 clones that had a .308 rifle spring installed instead of the 9mm spring. It seems that switching over to the 9mm spring greatly helps cycle the weapon better and extractions/ejections improve as well. This can also be used on any of the standard (91,93,94, etc.) rifles/pistols that don't use a pinned hammer/strut pair, as it doesn't require hammer removal from the trigger pack.

    Now remember, this can vary a bit. But the numbers are far enough apart that it should still be easy to tell which one it is, especially if you have some calipers.

    .308 Rifle Spring:
    Length, 2.4"
    Strand Diameter, .05"

    9mm Spring:
    Length, 3.1"
    Strand Diameter, .04"

    So now that we can see what the differences are, it might be time to change them...

    It's pretty easy and all you need for tools is a philips screw driver and a small "L" shaped allen wrench. Please note, you don't use either of these tools for their original designed purpose, but they just happen to be perfect for the job.

    First thing you do is remove your lower from the gun and let the hammer forward to unload the spring as much as possible. You can then use the tip of the screw driver to push down and reward against the hammer strut, then bring it up to allow it to push forward and up. Then you can just extract it right out of there. But before you do all this, make a point to see where the strut shaft sticks through the rear of the metal pack. There's a hole there.

    Now you just slide the new spring on and work it down and reward. Now this is where it gets tricky, but not too bad. There is a cross support right in your way so that you can't just push the pointy end of the strut through that hole, and the 9mm spring is a bit longer than the .308 rifle spring so it takes a little bit of coordination. Ok, so now you get to use the end of the allen wrench as a little hook. As you are pushing the "U" end of the strut down and compressing the spring against the metal pack at the rear, use the hook of the allen wrench to pull the strut point up toward the hole, underneath that cross member.

    It will take a little playing around with it (took me about 5 minutes on mine the first time) but you will eventually get it through there. Now that I know how to do it, it only takes about a minute.

    ETA: The previous step can be made even easier by removing the trigger pack from the lower grip. That would allow you to push something up from the bottom, into the pack, to more easily align the strut point with the hole at the back of the pack. But either way will work fine.

    But I re-iterate, please make sure you gotta really do this before going to the trouble. It might be interesting just to try a different spring anway though.
    "Sometimes change sucks."- Anne Frank

    Reloading: A low impact exercise with a high impact payoff.

    Take your wife or GF to the range more. If you want her to get the bug, you've got to expose her to the disease.

  2. #2
    CZ-75's Avatar
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    I stickied it! ;)
    Common sense isn't so common anymore...

  3. #3
    Requiescat in Pace
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    The black plastic pin pusher for AR15 (and HK clones ;-) has a handle that is the length of the rifle hammer spring and the handle plus shaft is the length of the 9mm spring - never leave home with out it.

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    kwesi's Avatar
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    John: sent you a PM.

  6. #5
    Really liking this HK Stuff Member

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    Default I replaced the spring myself

    Thanks for the sticky. I just replaced it myself. It took me 30 minutes. The 9mm spring was longer than the .308 so the fit was tight and took some time to re-assemble....But I did it all by myself. Thanks again for the detailed information.

  7. #6
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    Just wanted to say thanks for this post!
    Mark 23 AAC Ti-Rant
    USP9 Match Hybrid Trigger
    Bobcat BWF FSA Form 1...Ghillified

    Other stuff too.

  8. #7
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    Huge thanks to retrodog, threads like this make the internet the greatest tool ever. The hammer spring replacement fixed my bobcat.

  9. #8
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    so what about the grey hammer springs? are they no different than the 9mm ones in spring rate?

  10. #9
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    Quote Originally Posted by JeepGuy79 View Post
    so what about the grey hammer springs? are they no different than the 9mm ones in spring rate?
    I think the grey ones are the .40cal

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