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Discussion Starter #1
Riddle me this.. with that formula (USC plus full UMP kit as sold by various vendors) ... will that be everything needed for the conversion - I'm guessing yes - but the most important part of the question - will it shorten the process and remove a majority of the machining?

Does anyone have a rundown of steps given a full kit purchase?

One location I found that had a kit shows this (supposedly everything but the receiver). Given that, what has to be done to make the USC receiver work? (also I assume that's the upper receiver they mention).



Options-wise, this looks like it includes an SBR and a 3-mode selector - will that have everything required to do a full auto conversion, or do I have to gut the semi equipment from the USC and move them.

Sorry if these are fundamental to all here, but I really want to look at doing this project - just not sure what's truly involved (and yes been reading for weeks).

Cheers!
 

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Discussion Starter #2
I'm sorry - one more part to the question - if I wanted to leave the 15" barrel, are they interchangeable with the SBR - without doing any other work, or would that be very involved?

Cheers again!
 

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Wig,

First off...if you are not LEO, or Military, there is no way for you to legally convert a USC into a full auto UMP. Full auto sears and lowers that are made before 1984 are available for HK94's/MP5's...but the UMP is way too new to have any fully transferable parts available for it.

The only parts you would need from a UMP kit like you have pictured are the barrel, folding stock, and lower receiver. The bolt that comes in the USC will be fine to use in the conversion...or you could use the UMP bolt from the kit with just a little modification. Either way, thats up to you and you will still end up with an extra bolt that you could try and sell. You could also sell the short UMP barrel if you plan on sticking with the 16" USC barrel. If you decide to do that...let me know as I'll pay a good price for it! =O) The kit won't do anything for making the conversion work any easier aside from allowing you to get all the UMP parts you will need in one purchase.

When you send your USC rifle and UMP parts to have a conversion done, the person doing the conversion will have to do the following:

- Transfer the semi-auto USC fire control group into the UMP lower receiver
- Cut some material from the front hooks on the UMP lower so that it can attach to the USC upper receiver
- Mill the fore grip vents in the USC upper to match the look of a UMP
- Create a "Stock Block" that allows the UMP folding stock to fit with the USC upper receiver
- Widen the magazine opening in the USC upper receiver so that the wider UMP mags can fit into it.
- Engrave your personal information into the upper receiver if you plan on registering the gun as a Short Barrel Rifle with the ATF. (Not needed if you plan on using the standard 16" USC barrel)

Also, yes you can swap between the short UMP barrel and the stock USC 16" barrel if you want. All you have to do is knock out one roll pin in the receiver and the barrel will come out...takes about 5-10 minutes.

I think thats everything. I used Ed at www.hdps.org and would Highly recommend him for a conversion...he did fantastic work on mine.

Good luck!

-Mike
 

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Discussion Starter #4
Thanks tons for a detailed writeup. The first part's a deal killer - :( so it really boils down to mag capacity and looks.

All that being said, for the sake of a full-circle education, if I happened to be a SWAT member and bought said kit, took a USC - left the UMP kit parts as is - is it a plug and play with no modding? That's what I keep having rattle around in my head. Since I can't certify it - it's a non issue, but for personal gratification would love to know.

Thanks again!!
 

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Wig,

Glad I could help. As far as your last question...I think that in order to have an actual UMP bolt work in the USC upper receiver, some very minor work has to be done to the bolt but I'm not quite sure exactly what has to be done. Also, the plastic hooks on the front of the UMP lower that holds it to a UMP upper have to be enlarged to fit with a USC upper so the kit wouldn't be an exact match right from the start. Really the only thing that is a dead match between the UMP and USC is the barrel. Most of the other parts need minor fitting work.

-Mike
 

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Putting a fullauto lower on a USC would be a really really really bad idea.
You would have to cut a notch in the upper receiver for the auto sear, and once you do that you have just created an illegal machine gun.
Having it isnt worth the prison time, Swat team member or not.
:)
 

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If you are SWAT shouldn't you already have plenty of full auto stuff to play with without having to ask about how to do illegal conversions? Seems like more and more "law enforcement" personal don't really know the laws?
-Jason G
 

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Law enforcement and military aren't even allowed to convert a USC to full auto. A class 2 with intent to sell could but I don't see that making any sense......
 

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Discussion Starter #9
EASY fellas. I said "IF" as in hypotehtically. Of course higher-end mil/pol folks can get whatever they need (given taxes :) ) without hacking. I was just trying to understand how this all goes together. I'm an engineer - and love to understand the full depth of a situation.

Thanks again - and Mike, that's about the conclusion I came to on my own.

Best.
 

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Generally you do NOT want to use the UMP B/C in a USC. It takes a bit of modification (you need a mill, or the best dremel skills in the world), and it does not work with USC barrels.
 

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Wig,

First off...if you are not LEO, or Military, there is no way for you to legally convert a USC into a full auto UMP. Full auto sears and lowers that are made before 1984 are available for HK94's/MP5's...but the UMP is way too new to have any fully transferable parts available for it.

The only parts you would need from a UMP kit like you have pictured are the barrel, folding stock, and lower receiver. The bolt that comes in the USC will be fine to use in the conversion...or you could use the UMP bolt from the kit with just a little modification. Either way, thats up to you and you will still end up with an extra bolt that you could try and sell. You could also sell the short UMP barrel if you plan on sticking with the 16" USC barrel. If you decide to do that...let me know as I'll pay a good price for it! =O) The kit won't do anything for making the conversion work any easier aside from allowing you to get all the UMP parts you will need in one purchase.

When you send your USC rifle and UMP parts to have a conversion done, the person doing the conversion will have to do the following:

- Transfer the semi-auto USC fire control group into the UMP lower receiver
- Cut some material from the front hooks on the UMP lower so that it can attach to the USC upper receiver
- Mill the fore grip vents in the USC upper to match the look of a UMP
- Create a "Stock Block" that allows the UMP folding stock to fit with the USC upper receiver
- Widen the magazine opening in the USC upper receiver so that the wider UMP mags can fit into it.
- Engrave your personal information into the upper receiver if you plan on registering the gun as a Short Barrel Rifle with the ATF. (Not needed if you plan on using the standard 16" USC barrel)

Also, yes you can swap between the short UMP barrel and the stock USC 16" barrel if you want. All you have to do is knock out one roll pin in the receiver and the barrel will come out...takes about 5-10 minutes.

I think thats everything. I used Ed at www.hdps.org and would Highly recommend him for a conversion...he did fantastic work on mine.

Good luck!

-Mike
great info thanks! if you dont mind what did you pay for the conversion?
 

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You really don't need to buy a UMP parts kit to do the USC/UMP swap. Most of the parts will never be used.

All you need is the fallowing:

HK USC $1375.00 roughly.
HK UMP Stock $120~185
HK UMP Stock Pin $5.50
HK UMP lower $235
HDPS Stock Block "B" $185

This will give you a working gun. However there are a couple steps to making it legal. You have to register as an SBR which will allow you to use the 7.87 inch factory HK UMP barrel and you will need no 922r compliance parts or you need 922r compliance parts. You need three of the fallowing:

US made trigger
US made sear
US made magazine follower
US made magazine floor plate
US made barrel

If you use magazine parts as 922r compliance parts, you need both parts for EACH magazine you own. If you get caught with any HK factory magazines that do NOT have both compliance parts in them, you are in violation of the law. Keep in mind this only applies for people using these are complaince parts.

Personally, I didn't want to spend $300 dollars on a US made barrel, I wanted to keep my HK factory 16 incher and I can't legally register as an SBR here in my state so I needed compliance parts.

I personally am using the fallowing:

HDPS US made trigger
HDPS magazine floor plate $9.00
HDPS magazine follower $18.00

I can't comment on how much the HDPS US made trigger cost yet, I don't want to release that info and make Ed at HDPS mad. :)

I will need 4 of both of the floor plates and followers because I have 3 more magazines coming this week, giving me a total of 4 factory HK UMP mags.

If the project seems like too much of a pain in the ass or you simply cant do it, email Ed at www.HDPS.org for more info.

Any costs above and beyond what I've given above is extra's like more mags, rails, or labor if you can't complete this on your own.
 

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There's no shortage of screwed up UMP lowers with mis-machined hooks out there. It isn't as easy as some might lead you to believe. If it's too loose, too tight or not equal on both sides, you're probably going to have function problems.
 

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There's no shortage of screwed up UMP lowers with mis-machined hooks out there. It isn't as easy as some might lead you to believe. If it's too loose, too tight or not equal on both sides, you're probably going to have function problems.
It certainly isn't as hard as some might lead one to believe either. I have one that's loose and not equal on both sides and it works just fine - no failures of any kind. Anyone's welcome to check it out or shoot it if they see me at the range and want to try it out for themselves.

In theory, the concept isn't much different from an AR and everybody knows the fit of the lower to the upper doesn't have to be super tight on those. I have several AR's that have sloppy lower to upper fits that rattle and move - no problems with those either.
 

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There's no shortage of screwed up UMP lowers with mis-machined hooks out there. It isn't as easy as some might lead you to believe. If it's too loose, too tight or not equal on both sides, you're probably going to have function problems.
No it's really that easy... I've never build any gun before in my life. I've stripped my AR-15 but thats as close as I've come to building something.

The USC/UMP was so simple to put together. I was very surprised. For the hooks I just used a round file and did very little filing, test fit it. Filed some more, test fit. Filed some more, test fit and so on until the hooks fit.

You have to take off the same amount of material on all sides of the hook so if you do it by hand, just file evenly and you wont screw up.

Under filing is better then over filing. Ed from HDPS said a very slight amount of spring pressure is just fine.

The hardest part was transferring the trigger controls from the USC lower to the UMP lower. I did get stuck there but Ed from HDPS walked me threw it on the phone. Not saying he would have time to do that for everyone but I gotta say he is one helpful guy.
 

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If you use magazine parts as 922r compliance parts, you need both parts for EACH magazine you own. If you get caught with any HK factory magazines that do NOT have both compliance parts in them, you are in violation of the law. Keep in mind this only applies for people using these are complaince parts.
Are you saying that to count as one part you need both the floorplate and the follower? I was always under the impression that each of those counted as one compliance part???

BF
 
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