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And so it begins: 9mm USC to 16" UMP Conversion and links to ALL UMP Conversion Info!

85472 Views 117 Replies 37 Participants Last post by  Gokoolab
And so it begins: 9mm USC to 16" UMP Conversion and links to ALL UMP Conversion Info!

Well I *think* I’m the first person to undertake this particular conversion although I believe others have already done the 9mm UMP conversion with the 8” Barrel (feel free to chime in here guys! :)).

My main purpose here is to actually create a place with ALL the links and other information needed to complete a DIY USC to UMP conversion of any caliber.

First let me say this article is in NO way to say that you should not use any of the vendors that offer this conversion, rather than simply a place to find links and other pertinent info for those of us who really enjoy cutting up a brand new gun :D

Links to Machining Information for Conversion:
A VERY Basic Guide, read this first to get an idea of what needs to be done:

A VERY DETAILED Guide, read this when you have your parts and are ready for specs!

UMP Foregrip Vent Location:

UMP Mag Well Template

UMP/USC Parts Comparisons (See Gallery)

NFA Information that may be helpful when doing conversions:

Links to Suppliers for Conversion Parts (The ones I personally used)
Adam Webber HK4Evr
Top Notch Parts
Other Suppliers of Note:
Gordon Miller -
Phil Flack - [email protected]
Clyde Armory -

Now that I’ve got the basics out of the way I’m going to document what’s needed to do this conversion AND change calibers. I couldn’t find a lot of the information I needed easily such as how much I needed to change the bolt, 16” barrel suppliers ect. Let me start off by saying that while the regular 45ACP UMP conversion is actually very reasonable if you buy parts from the suppliers listed above, changing calibers can be VERY EXPENSIVE; you have been warned :D

Caliber Specific Conversion Parts:
Bolt Assembly

I bought all of the above parts (and parts for all my other guns) from Adam Webber ( and I can’t say enough about him and his service; amazing! Now before you go and call/email/homing pigeon ect Adam, he doesn’t have any more 9mm parts but does have plenty of 45 and I believe even some 40 parts. I will warn you that in my experience the 9mm parts may as well be made from un-obtainium as I had a HELL of a time finding ANYTHING in 9mm.

By now you are asking "Why the hell would he want 9mm?" Well the answer is relatively simple; I like 9mm :) All of my other guns (with the exception of the AR) are 9mm.

I was able to find ONE supplier that made a handful of 16” .40/9mm barrels and that was Top Notch. According to the gentleman I spoke to when I ordered he believed I was the first to buy one of the 16” units but still had a few left. I also bought an 8” HK barrel from Adam on the odd chance that someday Michigan will allow SBR (HA!).

The Parts:
HK 8” UMP 9mm Barrel, 9mm Magazine, 9mm Bolt Group (.45/.40/9mm all use the same recoil rod BTW) and some extra barrel pins.

Now that I’ve got these parts I’ll start to document what you need to do to the bolt to assemble this thing as well as updating this when my 16” Barrel arrives and how the gunfunctions/looks ect. I hope this post will help some people not have to search for hours to find information like I did!
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