Collapsable HK Stock Build

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  • schnejerator

    dabbled in pacifism once
    Sep 26, 2014
    116
    haggistucky
    Well I figure NFA thread since... well who else would want to mess with an A2 stock on an HK?

    Anyway, I have post SB281 Form 1 for my HK94 and 53 clones. Normally, they would come in at about 26.75 and 28.25 inches respectively when SBR'd with an A2 stock. There are some other solutions with AR receiver extensions, but I wanted something different and not folding (so flash hiders and suppressors are OK). I've only built one so far, for the 94.

    And yes, I cut my German A2 apart for this science project. Thanks Frosh!

    The design allows pushing down on the spring loaded pin of the side of the stock to release the butt pad to slide in or out. The mechanism itself works pretty well, slides with little resistance. Spring is a bit stiff, but still operable one handed... and this means it is a nice positive lock. Currently I just have it drilled for two locations, full open and full closed.

    It still needs some cleanup and final fitting/trimming. More importantly finish the aluminum pieces with a nice, super evil matte black.


    Here are the telescoping tubes before trimming:
    1.%20Tubes.jpg


    Test fit of the delrin plunger and spring assembly:
    2.%20Mech.jpg


    Test fit of the buttplate adapter:
    3.%20Plate.jpg


    LOP checkout on the HK94 clone (2.5" of extension):
    4.%20HK94%20Sized.jpg


    LOP checkout on the HK53 clone (1.0" of extension):
    5.%20HK53%20Sized.jpg


    Butt plate fitting around the adapter:
    6.%20Buttplate.jpg


    Closed position:
    7.%20Closed%201.jpg


    Closed position (again):
    8.%20Closed%202.jpg


    Open and locked:
    9.%20Open.jpg


    SB281 compliant :party29::
    10.%20HK94%20OAL.jpg
     
    Last edited:

    Hawkeye

    The Leatherstocking
    Jan 29, 2009
    3,971
    That's a fantastic idea, and something similar could really help all the people who'd like to SBR one of the Zenith clones.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,963
    Burning the midnight oil I see. Nice work. Thanks for sharing your alterations with the rest of us. That is really cool!
     

    smdub

    Ultimate Member
    MDS Supporter
    Nov 14, 2012
    4,659
    MoCo
    That is seriously clever! Exceptional job. (from a fellow amateur machinist)
     

    wbw2123

    Active Member
    Nov 19, 2012
    905
    Awesome work. That is a great idea. I see many more hk sbr's in MD as a result of your creativity. Thanks for sharing.
     

    fred333

    Banned
    BANNED!!!
    Dec 20, 2013
    12,340
    I actually posted the second response in this thread, but my computer locked-up just as I hit the Post button. Not sure what happened there, but very clever idea. Good old American ingenuity.
     

    schnejerator

    dabbled in pacifism once
    Sep 26, 2014
    116
    haggistucky
    Thanks for the feedback. These kinds of things are even sweeter when you get to give a big middle finger to senseless rules (maybe we should keep that on the down low before they ban creativity).

    I'll tell ya when I first started cutting that stock apart I was thinkin "this sh!t had better work..."
     

    protegeV

    Ready to go
    Apr 3, 2011
    46,880
    TX
    This could be a revolutionary thing. So many other possible applications. Tavor, ps90, etc...
     

    pilotguy

    Ultimate Member
    Jan 12, 2009
    1,385
    Woodstock, MD
    For your HK53 you could use an HK33A2 stock to get your length. Also with the factory sliding stock extended and flash hider it should comes in at 29.7" OAL.
     

    smdub

    Ultimate Member
    MDS Supporter
    Nov 14, 2012
    4,659
    MoCo
    For your HK53 you could use an HK33A2 stock to get your length. Also with the factory sliding stock extended and flash hider it should comes in at 29.7" OAL.

    An HK33/93 A2 stock comes up short. His measurement is correct (I went and double checked as I have a 53 SBR too.) Can't include the flash hider unless it's pinned. A rifle stock is easy to put a spacer in since the buttpad snaps on.
     

    smdub

    Ultimate Member
    MDS Supporter
    Nov 14, 2012
    4,659
    MoCo
    Mine both have pinned HK53 flash hiders and they are 29.7". This is also the factory HK OAL measurement.
    Yes, HK factory OAL includes (removable) flash hider but there is *NO WAY* I'm pinning anything on my real 53 barrel. A simple stock spacer is no big deal.

    I wonder if you could do something similar with the PS90?
    My wheels are already turning on this. Anyone have a pic what the end looks like inside w/ the buttpad off?
     

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