CA-compliant UMP 9mm conversion
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Thread: CA-compliant UMP 9mm conversion

  1. #1
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    Default CA-compliant UMP 9mm conversion

    Hi folks,
    I just picked up a USC (my first gun) after thinking about it since they were re-released last summer.

    I wanted to run my [potentially] idiotic, [definitely] expensive, and [certainly] unnecessary UMP 9mm conversion process by you all for comment.

    My understanding is that the UMP conversion is CA-legal as long as I disable the folding stock and introduce at least 3 parts as per 922r, in addition to keeping 10rd mags.
    There's a bunch of assumptions here, so please let me know if any of these are incorrect.

    1) Buy UMP conversion parts from HKParts: FBI lower, HDPS stock block, folding stock
    2) Swap in TCG from my USC, modify hooks as per DIY. Install USC grip-blocker.
    3) Send the upper out to get modified, including HDPS sear or tommybuilt trigger (+1 922r for either)
    4) Disable the folding stock operation as per DIYs on this forum.
    5) Install the 10rd blocker into the UMP 25rd mag (with 2 parts from the 3-part compliance kit, blocker replaces one of them - +2 922r net).

    At this point it would be a fully functioning and CA-legal UMP conversion, correct?
    Step 6 is the dumb one:

    6) Buy the 9mm conversion kit from HKParts (+2 922r) and install barrel, block, and mag (with 10rd plate)

    Is this accurate? Thoughts? Thanks!
    Last edited by Goodguy11; 06-24-2019 at 10:57 PM.

  2. #2
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    dude let me know where you get some mags at. I cannot find any.

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    Quote Originally Posted by revco33 View Post
    dude let me know where you get some mags at. I cannot find any.
    HKParts has the US-made UMP 25rd mags in stock.

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  5. #4
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    The only California compliant USC is the featureless model. If you change back to a pistol grip, you would be breaking California gun laws and assembling an assault weapon. Featureless means no pistol grip, no thumb hole stock flash hider, no folding stock, no bayonet lug, no forward pistol grip, and no grenade nor flare launcher. With featureless, you can still use the regular magazine release. I suggest that you check with calguns.net and I am certain the more knowledgeable forum members will agree with my comments.

    CA-compliant UMP 9mm conversion-11041_1_.jpg

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    Quote Originally Posted by BitterOldMan View Post
    The only California compliant USC is the featureless model. If you change back to a pistol grip, you would be breaking California gun laws and assembling an assault weapon. Featureless means no pistol grip, no thumb hole stock flash hider, no folding stock, no bayonet lug, no forward pistol grip, and no grenade nor flare launcher. With featureless, you can still use the regular magazine release. I suggest that you check with calguns.net and I am certain the more knowledgeable forum members will agree with my comments.

    Click image for larger version. 

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    He's fine to change as long as it's featureless like you described.

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    Quote Originally Posted by Socalmp5 View Post
    He's fine to change as long as it's featureless like you described.
    I just checked and the USC grip-wrap does not fit the smaller UMP grip.
    I'll order a custom one from Featureless Fin Grips

    CA-compliant UMP 9mm conversion-b62ba25986798973f1bbd1c9eab7b37f.jpeg

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