HK USC to UMP conversion

Nemo said:
Oh! OK!;)




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Yeah I was pretty sure you owned one, which Is why I was givin ya a hard time on the rounds :D
 
re:USC to UMP

Just bought the last HK USC from Wild West Shooting. Great price too. Very good service as well!

Now comes the conversion process. This thread is a wealth of info and inspiration for what I am about to undertake. I will start off with simple rails and the short barrel for now. In the near future I will try to obtain the parts necessary for actual lower conversion.

I am hoping to get the lower already prepped to hang on the upper.
 
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rajczak_kashka said:
Just bought the last HK USC from Wild West Shooting. Great price too. Very good service as well!

Now comes the conversion process. This thread is a wealth of info and inspiration for what I am about to undertake. I will start off with simple rails and the short barrel for now. In the near future I will try to obtain the parts necessary for actual lower conversion.

Anybody know a good smith in the Vancouver/Lower Mainland who could notch the air vents for the barrel in the reciever?

I am hoping to get the lower already prepped to hang on the upper.
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Its not that big of a deal to make the mods. Just take a 1/4" round file, and slowly open up the hooks until it fits snugly (not too tight, but not loose) onto the USC receiver pin.

Swapping the guts is pretty simple, any gun smith should be able to do it. It really only goes together 1 way.
 
rajczak_kashka said:
approx how much do they have to be opened up?
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Not much at all. the factory HK USC pin is something like 7mm diameter (just checked to make sure), and the UMP "hooks" have a 6.5mm hole. so it needs to be opened up by a 1/4mm all the way around (or 1/2mm in diameter bigger)

It took me maybe 15 minutes with a 1/4 inch round file to do it. Just make sure you look at it, and if you see metal on the inside of the hooks then stop working in that area. Its not gonna kill it if the metal is exposed but that's as far as you want to go in that area. Check the fit often, you can do each side by testing the hooks on the opposite "pin" on the receiver, to see if it fits or not.

If you really want a machinist to cut the vents, it shouldn't be too much, but you can also use a 6mm drill bit to drill the holes, then score lines (or use tape) that match the holes up, and then use a dremel tool with a cutoff wheel to open up the vents. Cut a bit on the inside of the vents so you can clean it up after with a file.
 
A dremel for the cooling holes? Raptor you must have steadier hands than I...lol

I would probably be more inclined to have someone with a milling machine do this as to not wreck the upper.
 
If it was my HK USC I would get a machinist or a gunsmith to do it. Its not that hard to do if you have all the tools. There is a gunsmith in Delta but not sure how good he is.
The information for the vent holes were posted earlier in the thread.
I recenty got a HK USC also had the vent holes done. I was thinking of doing the vent holes myself but decided to let a machinist do. The risk is not worth the gamble if you make a mistake.
 
mrsmitty said:
After over a year and half of source parts a ton of money and acquiring a black HK USC 45 carbine I have finally completed my UMP conversion. The conversion was done by Ian at Herron Arms. He does excellent work. The conversion has all 5 cooling slots cut into the reciever and sports the UMP FBI lower with HDPS stock block, barrel is 7.87 inch Green Mountain UMP barrel and the rest of the parts are all genuine HK. Here are the pics they were a rush job so not too detailed. I might take some better photos tomorrow or friday when I have more time.

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Holy cow, it looks exactly like mine, right down to the parts detail. I put an Eotech on mine.
 
rajczak_kashka said:
A dremel for the cooling holes? Raptor you must have steadier hands than I...lol

I would probably be more inclined to have someone with a milling machine do this as to not wreck the upper.
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I did my vent holes with a 1/2 inch drill bit. I did 5 offset holes like the SIG CQB handguard, so I never tried the dremel tool method.

I guess for what it costs to have a smith do it, it wouldn't be all that much money.

Just snapped a pic for clarification. This actually took a REALLY long time to do, had to go from 1/8th inch all the way to 1/2 inch in 1/32 increments, and measure distances each time to make sure they stayed exactly on target. Turned out awesome though.

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yes,it did turn out good. I have heard that a gunsmith would charge about $100 to do the slots. With the drawing for hole placement that is posted here it should cut the costs down a bit as there is no mystery as what to do or location of slots.
 
rajczak_kashka said:
Found this site with some good info and instruction as well:
http://www.texassmallarmsresearch.com/TechInfo/HowToUMP/HowToUMP.htm

What has to be done exactly as far as "permanantly block off auto sear area"? Some detailed info would be good and appreciated. Would this be still be necessary with the semi auto only FBI lower?
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You dont need to do it, but I did anyways.

When you get the FBI lower (semi-auto only) or even if you got a Navy lower (full-3rnd burst-semi-safe) or whatever it is, the auto sear has its own little "spot" with its own pin.

Now in Canada it doesn't matter because as long as you dont cut into the receiver of the USC, it wont take the sear anyways. But what many people do, it tape off the area, and then fill it with epoxy to fill in the entire void.

I did this (filled with epoxy) after cutting a small triangle cut halfway into the extra pin, then put it in and filled it with epoxy. This way it cant come out, and the pin cant come out either....

Again, absolutely no reason to do it, other than to do it.

Heres a pic from HDPS showing what is changed:

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Notice, its the box space right behind the mag well and mag catch area. I made a little "box" out of cardboard that just fit into the space that is machined out in the pic, then put some gun oil on it, and then filled the void with epoxy. That way, the little box came right out once the epoxy was semi-cured, and left a perfectly smooth face.
 
Thank you so much sir.....this is exactly what I wanted to see as I do not have the USC or UMP lower in my hands yet. I may just leave it alone and simply enlarge the hook holes to attach to the upper and away I go.

Again.....thanks Raptor
 
rajczak_kashka said:
Thank you so much sir.....this is exactly what I wanted to see as I do not have the USC or UMP lower in my hands yet. I may just leave it alone and simply enlarge the hook holes to attach to the upper and away I go.

Again.....thanks Raptor
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no problem :D

I wouldn't mess with the sear area unless you really wanted to do it. Im just weird like that, so I had to do it :p
 
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