Please click the READ MORE below to read the article about the HK USC to UMP 45 conversion.  Please note, this conversion may or may not be legal in the State you live in.  It is your responsibility to ensure this is legal to do in your area.  I have made this new video as a follow up to the series of fragmented videos covering the USC to UMP conversions.  Also, since the HK USC to UMP was one of the first videos that I did nearly 2 years ago (hard to believe I have been doing these for 2 years now), I felt based on the requested information about this, that it would best to re-do these videos into a single video that hopefully covers other questions I have had about this.

HK USC to UMP Conversion

by Jessie Indracusin


This has been the most popular discussion I have had in both viewers and questions.  I wanted to re-produce these videos now that I have been a little wiser in this whole process of video production and the fact that YouTube moved to Hi-Def from when I first produced these videos.  Your first thing to note is the cost.  This is a HIGHLY expensive project.  If you don't want to spend the money to do it right, I would recommend you steer clear of it.  I will cover what is needed for this project in this article.  You can expect to pay anywhere from $3500 to $3800 to do this project.  This will very based on optics, cost of parts and if you do the minimal modifications to the upper receiver on your own or pay someone.  With that, let's get right into it.


You will need the following before you start this project (Note prices are all subject to change):

1) HK USC Carbine (preferrably Black Edition versus Grey) $1700 to $1900

2) HK UMP US Made Trigger (Compliance Part) $125-$145

3) HK UMP US Made Floor Plate (Compliance Part) $10-$15

4) HK UMP US Made Follower (Compliance Part) $20-$25

5) HK UMP Rail Blister Pack (4-Rails) $125-$150

6) HK UMP Stock Block Rev B (Compliance Part) $195

7) HK Roll Pin $10

8) HK UMP 45 Magazine $85-$115

9) HK Folding Stock $125-$150

10) HK UMP 45 FBI/Multi Selection Lower Receiver $295-$495 (This is whatever lower you want for the gun.  At the end of the day, after the conversion, the only option that will work will be semi-auto)

11) Forward Pistol Grip $25 to $50

12) Holographic Optics -Eotech 512 or similiar $350 to $399

Strip it down and build it

Keep in mind, after you do this work, there are a lot of parts that will become useless.  For example, when you buy the lower receiver, you will be taking out nearly every part from the lower and junking it.  You are using the internals plus the new trigger and putting it into the UMP 45 lower.  I can not offer you any specifics on removing the USC lower components and putting it into the UMP lower.  The video would take forever and would include a LOT of cursing.  The key to doing this correctly is to take as many pictures as possible of the lower of both.  CAREFULLY take the parts out of the gun and place the pieces as they sat inside the lower so as to know the position they go back into the gun.  Unlike the H&K MP5 series which has the entire trigger group pulls out simply and places into another lower, the UMP is not that way.  This is a design failure of HK in my opinion, but since you only would ever do this once, I consider it just a major inconvenience.  

Watch the video to see the specifics of widening the magazine well on the upper receiver.  This is required in order to slide the larger double stack 25-round magazine of the UMP 45 versus the older single stack 10-shot magazine of the USC.     The width of the magazine well needs to be widened to just a hair short of 1.25".  I recommend doing this modification carefully and in stages so that you widen the well until it snuggly fits the magazine.  I don't really think there is an exact measurement.  I kept cutting the upper area of the receiver until the magazine fit correctly in the gun.  The video explains this portion a lot better.

Things to look out for

Make sure you go with a stock block that uses a pass through bolt (a bolt that goes perpendicular through the stock block and not just two screws that screw into a stock block.  This is the reason.  I originally had the first revision of these stock blocks that utilized the factory HK screws that came in the USC to work with the stock block.  The screws will actually strip and warp the stock block and fall out of the sides if you decide to fire the gun with the stock folded.  We found out the added recoil of the bolt system causing impact to the stock block meant all the stress was put on the two screws.  The two screws are NOT capable of handling it and will strip the opening on the stock block.  The bolt that goes through the stock block and screws off on the end is a superior design and you can fire it with a folded stock all day.


I hope I both discourage and encourage people to do this.  I want to discourage people who want to try and do this on the cheap but yet encourage people who are willing to spend the money.  This IS worth the money.  I shoot this gun more than any other gun I own and is the centerpiece to my collection.  It brings the most questions when I bring it to the range and a very unique gun.  I hope this one article and video helps answer a lot of questions that everyone has written and a single comprehensive video and article.

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Last Updated (Sunday, 18 April 2010 18:29)