UMP to USC lower conversions - costs and who? - Page 3
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Thread: UMP to USC lower conversions - costs and who?

  1. #21
    RPG
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    Quote Originally Posted by kbinmt View Post
    milling the bolt so that it fits in a semi receiver. The material that would have engaged the catch is removed.
    @AviatorDave and @tbostic both provide this service.
    Hi, just wanted to point out so no one is confused:

    Removing that material from the underside of the bolt does not prevent engagement of the auto sear, the auto sear is tripped by the pin at the back.

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    Quote Originally Posted by RPG View Post
    Hi, just wanted to point out so no one is confused:

    Removing that material from the underside of the bolt does not prevent engagement of the auto sear, the auto sear is tripped by the pin at the back.
    Correct. The extra material in the UMP bolt is only there to prevent installing it into a USC receiver. Not really sure why, as without the notch cut out in the receiver for the trip lever, it wouldn't allow fa fire anyways.
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  3. #23
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    Quote Originally Posted by RPG View Post
    Hi, just wanted to point out so no one is confused:

    Removing that material from the underside of the bolt does not prevent engagement of the auto sear, the auto sear is tripped by the pin at the back.
    Thanks for catching that.

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  5. #24
    RPG
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    Does anyone have numbers on how much material needs to be removed from the hooks on a factory lower to fit a semi upper receiver? I was thinking of trying the lower conversion myself.

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    Default UMP to USC lower conversions - costs and who?

    I use an 11/32" end mill. They are actually a short slot. I plunge through the center, then move the table all the way out of the hooks, then back to 0,0. I have a fixture that holds the lower at an angle so that the Y travel is parallel to the magwell.

    There are steel hooks embedded in the plastic. A tiny bit of the metal is machined out as well, maybe just .005"-.010 or so.
    Last edited by AviatorDave; 10-20-2017 at 06:31 PM.

  7. #26
    RPG
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    Quote Originally Posted by AviatorDave View Post
    I use an 11/32" end mill. They are actually a short slot. I plunge through the center, then move the table all the way out of the hooks, then back to 0,0. I have a fixture that holds the lower at an angle so that the Y travel is parallel to the magwell.

    There are steel hooks embedded in the plastic. A tiny bit of the metal is machined out as well, maybe just .005"-.010 or so.
    On second thought maybe I'll have a professional do it.

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    @AviatorDave I'm having a UMP clone built from an Omega Gideon Shadow receiver, but we're missing one last piece: the Heckler and Koch G36 / SL8 / USC Left Safety Lever (it's out of stock just about everywhere, atm). I read in the forums that you recut the UMP selector lever so it works with the USC internals. Is that a service you can provide? Can you PM details about that (new member)?

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    Default UMP to USC lower conversions - costs and who?

    Email me - Dave dot Akins at akinsprecision dot com. My pm's are several hundred over the limit and I haven't taken time to clear old ones out.


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    Emailed you, @AviatorDave

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