H&K USC/UMP Conversion

[DJTC45]

I bought this H&K USC 45acp last week. Got to reading and searching for some upgrades that I could do. I purchased a new Complete UMP Lower, Stock Block to add a Folding stock to it, XS Tritium Front Sight, and a few other things.

[DJTC45]

I got the UMP Lower fit to the USC Upper, I took a Round File and used the old USC Lower as a guide and marked it with some tape. Lightly filed the Hooks on the UMP Lower till I got it fit up to the USC upper, turned out pretty good, next will be enlarging the Mag portion of the USC Upper to be able to use the UMP Double Stack Mag  and lay out the Vents and figure out how to cut them and all that is left is to put it all back together and check functions before coloring the Grey USC Upper to Black to match everything else. So far it's been a good project, can't wait to get it done. I'm going to leave the 16"USC Bbl. for now still deciding if I want to go the form 1 route. Stay tuned for the finished project. Thanks for looking.

[DocHawk]

Nice work! I've done a few of these. Increasing the diameter of the lug mount holes is not for the faint of heart!

Note it's also possible to cut the receiver side rails at the magwell, to accommodate real UMP mags, too. That's a great mod to get you out of the nanny cap magazines.

[DJTC45]

That's what I'm working on now, almost got it done. I've got a UMP 25rnd Mag coming in with the stock block and a couple other things. I'll finish that up once it gets here. Now I just got to figure out the vents next.

[NoBanStan]

I've had the opportunity to shoot a USC and really enjoyed it. The only reason i never bought one is because of that frame. I'm very interested to see how this turns out.

[DJTC45]

3 hours ago, NoBanStan said:

I've had the opportunity to shoot a USC and really enjoyed it. The only reason i never bought one is because of that frame. I'm very interested to see how this turns out.

I hope it turns out good lol.... I'll post pictures of the project as it goes along and when the parts get in.

[DJTC45]

Got some more parts in today. Going to see about making a "jig" for cutting the side vents, I did the bottom slot without a jig and it came out okay, just a hair off but the rail will cover it, not perfect but pretty good for free hand. Going to work on the Mag well since I got one of the 25rnd UMP Mags in hopefully tomorrow. Pictures to be posted soon. Thanks for checking out my thread, it's been a fun project and learning lessons.

[DJTC45]

Got a few more parts in. Got the Mag Well inlarged to accept the UMP Double Stack 25rnd mags, it just needs cleaned up a little.

[DJTC45]

I then put the bolt in without the spring, attached the Lowe with the mag and a round in it and tilted the upper and lower downward and gave it a "jolt" by hand and it stripped the round off the mag and the bolt captured it perfectly.

[DJTC45]

Moved on to the Stock Block, had to do a little fitting to get it to slide into the UMP Lower. It fits nice and snug, all that's left is to install the stock and a few more little parts and cut the side vents put everything back together and function test it then color the upper black and this project should be done.

Edited November 2, 2023 by DJTC45

[DJTC45]

Update, got a few more parts in. Stock, 25rnd. mag. and a Mag Release Paddle made of aluminum and larger than the plastic one. 

[DJTC45]

I got everything installed and fitted up. Now all that's really left to do is clean up the vent slots and dye the Grey USC upper to match the lowere. I didn't pay attention to the router bit I used and they are larger than what the orginal ones should've been. Oh well live and learn, I installed the new aluminum mag release and it works as should. I then mounted the stock and I just had to do a little fitting on it to get it to fit the stock block. So far I'm pleased with the results except for the vent screw up. The second picture shows the size difference in the mag release's.

Edited November 13, 2023 by DJTC45

[Patriotsson]

Always the coolest "toys"! Nice work!

[DJTC45]

Thanks, I just wish that the vents turned out better but I'll clean them up. With the rails in place they cover enough of them but I have to even them out. Pictures to follow once I get it dyed, hope that turns out good.

[DJTC45]

Well here's the final product. The dye job came out pretty good, I was kind of surprised when I got it done matches the lower end pretty good. I might do another one in 9mm just got to round up all the parts.

[RED333]

Nice!!!

[DJTC45]

Thanks, it was a good learning experience for sure. Hopefully I can get the 9mm one going this spring.