Gun Review: Converting an H&K USC to a UMP

    It is no secret that H&K makes great firearms. They have been in business since 1949 and have produced a number of small arms that have been adopted by countless armies and police agencies across the globe. Perhaps the most famous however has been their MP5 series of submachine guns. The venerable MP5 fires from a closed bolt, which at the time was very unusual for a sub-gun, as open bolt firing had been the standard throughout the 20th century. The successor of the MP5, the H&K UMP or Universale Maschinenpistole was developed originally as a cheaper alternative to not only supplement, but replace the aging MP5s in police and military arsenals. Despite this, both weapon systems are still being produced, perhaps because the heavy proliferation and reputation of the MP5 has allowed the product to remain very profitable for Heckler & Koch.

    Prior to 1989 a civilian variant of the MP5 was available to the public, dubbed the H&K model 94. It was imported with a 16 inch barrel to comply with import regulations and to be exempt from NFA registration as a short barreled rifle. Many of these have been given selective fire capability with the installation of a legally registered full-auto sear as well, making the MP5 one of the most common sub-guns in civilian hands despite the high cost. The ’89 ban on the importation of non-sporting rifles to the USA stopped the flow of H&K roller locked firearms (aside from the SP89 which hung on until ’94), and also prevented civilian variants of the UMP from ever reaching our shores. It seemed that us regular folks would never get to lay our hands on a UMP until parts kits from demilled guns and a little bit of innovation allowed shooters to convert their H&K USCs into UMP configuration. The following is a step by step process on how to perform this conversion.

    First of course, you will need to purchase an H&K USC-


    Buy a UMP lower, stock, and a “stock block” which is a magnificent piece of machined aluminum made by HDPS-


    Enlarge these hooks on the UMP lower with a round file to allow them to fit over the USC’s slightly larger plastic pins-


    Attach the stock to the stock block with a stock axle pin-


    And throw it all together while being mindful of 922r-


    To do it right, you need to mill the front out to form the cooling ports. Ed at HDPS performs front end milling and will mill the mag well out to accept the larger UMP mags-


    Once you submit your form 1s, accompanying paperwork, and $200 check to the ATF and receive your tax stamp back in the mail, you are free to buy and attach your short barrel-


    The gun also works great, even when firing it as fast as possible:

    Storm also makes a delightful case that will hold the gun with an optic, odds and ends, and a total of six magazines!



    And that is it! The conversion is very simple and only requires a total of three 922r compliance parts (I used a barrel, mag follower, floor plate, and sear just to be safe). As for the cost of replicating this build, I have compiled a list of my costs:

    Gun- $1100
    Lower- $400
    Stock/block- $300
    Tax stamp- $200
    Barrel- $250
    Vent cuts- $50

    I also managed to sell my takeoff parts for $500 including the barrel, factory stock and lower, magazine, and buffer on a popular gun auction website. So all in all, I have approximately $1800 or so in this gun (sans optic of course).

    So it is not a real UMP and never will be, but it is as close as we civvies will ever get to owning one without becoming an SOT. But you may be asking yourself, how does it compare to an MP5? Well, a quick accuracy test provided good results-



    All shots were from 20 yards standing. So far I have put about 1500 rounds through this gun and it has yet to have any kind of jam or hiccup. I would highly recommend this conversion if you are in search of a fun project or a fun pistol caliber carbine!


    Alex C.

    Alex is a Senior Writer for The Firearm Blog and Director of TFBTV.