How to Convert USC to UMP

Heckler & Koch produces both the USC carbine and UMP. The USC is a civilian version of the UMP submachine gun. The primary difference is that while the UMP offers the option of fully automatic firing the USC is only a semi-automatic. Also, a UMP does not require any tools to field strip, while the USC does. Some gun enthusiasts have wanted to convert the USC to remove that limitation, making it more like a UMP.

Things You'll Need

  • HK USC Receiver
  • Dremel with milling bit
  • Black spray paint
  • HK USC Fire control parts
  • HK UMP Lower assembly
  • HK UMP Stock
  • HK UMP .40 Smith & Wesson Barrel and bolt assembly
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Instructions

    • 1

      Remove any magazine from the USC receiver. Hold a UMP magazine up to the seating point to visualize where you need to mill the opening so that this larger magazine can fit. Once you're done making the opening fit the new magazine, paint the receiver black to match what a UMP would look like.

    • 2

      Mill the front hooks on the UMP lower receiver so that they will fit the USC receiver, and install the fire control parts from your USC into the receiver. Use your screwdriver to loosen the hardware that holds the locking tab in place. If you want fully automatic firing, you'll have to use fire control parts from a UMP in your USC receiver.

    • 3

      Connect the UMP stock to the USC receiver, and then add the UMP barrel to the stock. Use your adjustable wrench to tighten the bolt assembly into place.