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wile326

HK USC to 10mm

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Has anyone converted an HK USC to 10mm? Seems like it has a lot of possibilities.

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It mags were plentiful it may be a different story. Its hard to justify the cost of modding an already expensive rifle when one could go to a AR in 10mm or an MP5-10 clone much easier. Nonetheless, it would be an interesting project.

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Hi guys,

 

Long-time lurker, first post. It is indeed possible to do a UMP conversion to 10mm, because I have done so. Be warned that it is neither a cheap or easy process, mainly because of the parts needed. That said, I will go through the steps and items needed.

 

First, obviously, you need a USC. If you don't already have one, they typically go anywhere between $1200-$1600 online. New style (black) or old (gray), doesn't matter.

Second, you need a grease-gun mag conversion lower from Top Notch Parts (Wade Bailey). These run about $250 from Top Notch, and take the internals of your existing USC lower. You will need to open up the magwell of the USC in order for the grease-gun mags to fit.

Third, you need grease gun mags. They are going for around $25-35 each these days. The mags need to be modified to fit 10mm by peening in the feed lips so that they hold the 10mm rounds securely.

Fourth, you need a UMP 40 bolt group, and it has to have some material milled off of one side so as to fit the USC receiver. HDPS can do the mill work on the bolts, and there are probbaly other folks out there who will do it too. You can get the bolts from Adam Webber at HKParts.net, or Gordon Miller at HKSpecialist.net, for around $500. Note that if you intend to do a full SBR UMP conversion, you are best off picking up complete 40 parts kit, which usually run $1200-1500.

Finally, the hardest part of the build, you need a 40 UMP barrel, which will need to have the chamber resized to 10mm. The two guys above occasionally have 40 barrels in stock, but again it may be best to buy a complete UMP 40 demill kit. As for the re-sizing, Jayson Cotter at Investment Grade Firearms did mine for around $80.

 

If you cannot use a factory UMP 40 barrel (you don't want to or can't do an SBR), then you can get 16" 40 barrels from Adam Webber, HDPS or Top Notch. I think TN makes all of these, I am not sure if HDPS makes their own or not. The factory barrels run around $450-$500, the TN 16" versions run around $250.

 

So you are looking at a minimum of between $2500-$3000 for one of these conversions, if you have to buy everything from the ground up. I started off wanting to do an SBR'ed UMP 40 conversion a few years ago, and had it built by Tactical Excellence. At some point, I started thinking about doing one in 10mm. What I found was that the UMP 45 mags do not have the right follower angle, nor can the feed lips be adjusted since they are plastic mags. In contrast, the UMP 40 mags have the perfect follower and lip spacing, but there are two rails inside the mag that are too high to allow the 10mm rounds to fit in the mag. I have tried everything I can think of to try and cut down these rails inside the mag, but the cut is pretty much impossible according to everyone that I have had look at it.

 

So that led me to try the TN grease-gun conversion. I have one of the BarrelXChange UZI 10mm conversion setups, which also uses the modded grease gun mags. I had Troy at BarrelXChange mod some mags for me, and they work 100% in my UZI and the UMP conversion. Rounds I have tested include Georgia Arms 180-grain and factory 175-grain Winchester Silvertip HPs.

 

In short, it's a doable option, but unless you truly love the UMP it's probably way more costly than most people want to go. Here is a pic of my multi-caliber UMP conversion setup. It can swap between 9mm, 40 S&W, 45 ACP and 10mm. It is in 9mm configuration in the pic. Note that the 2 40 bolts shown are identical, but one of the 40 barrels has been re-chambered for 10mm. The grease gun lower is not shown here.

 

DSC01016.jpg

 

 

Thanks,

James

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Well as it stands today I do not have the money for that, but I do like the Idea!

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