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Discussion Starter · #1 ·
I'm considering buying a MM 9mm USC/UMP kit ( as part of a possible larger caliber consolidation) and wanted to hear people's experiences with them.

What information I've been able to find only really discusses how some people needed their USC mag wells opened up a little more to get the Mags to sit properly, but not much beyond that.

So, what do you think of them? Have they held up and been reliable? How do you like the 9mm compared to the .45? And of course anything else you cared to share!

Thanks in advance!
 

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I have had two MM 9mm kits: one full auto kit for a post-sample UMP40 and a standard kit for a USC conversion.

MM F/A kit: The full auto kit required some tweaking due to some initial failure to feed issues and after speaking to Mike on the phone about it he asked me to send him the bolt. He performed some vert minor radius adjustments to the front edge where the bolt picks up the round from the magazine and it ran flawlessly for thousands upon thousands of rounds since then. At demo shoots we always provide a list of small arms that clients can sample and oddly the UMP was always choice #1 or #2, only taking second behind an M249 SAW. Demo shoots are high stress: people are paying to be there, and that UMP 9mm never disappointed. I also used the firearm in several subgun competitions and it never failed me there either. We recently sent the UMP along with the MM F/A kit to a new home and I was sad to see it go.

I don't even know if the full auto kit is still available and the amount of people here that could use it are very few. I'm just pointing out with this the fact that if it runs in full auto and does so reliably, you can be sure it'll function in semi-auto. Also, Mike's support of his products is OUTSTANDING.

MM Semi-auto kit: Same experience holds true with my Michael's Machines 9mm USC bolt and barrel kit in semi-auto. I've had this bolt and barrel for 3-4 years now I think. I have never had a single issue with the rifle. Aviator Dave cut the magwell (and barrel slots) and I use a HDPS stock block and a MM 9mm bolt and 7" barrel. This is the range toy that everyone wants to shoot. If I am ammo rich on a particular day I'll let a guest shoot a magazine of my ammo. If I am not, I hand them an empty magazine and tell them to load whatever 9mm they've got with them. It shoots everything including steel case without issue.

Honestly, for as much crap as people give HK for following up the MP5 with the UMP, it is a pretty reliable firearm, and the Michael's Machines 9mm kits keep that reliability going strong!


 

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I Bleed Urban Gray
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So I was thinking about this kind of conversion for my Aviator Dave UMP. I don't see that kit listed anywhere on his website or in his section. The conversion is "just" a new barrel and bolt group right? How much did yours run when you got it? Interested in your perspective because James' thought was that even in 9mm you get that hard recoil impulse of a blowback gun so his opinion was that it's not worth the money to convert to 9mm from .45 in a UMP. Essentially, if you want a soft shooting 9mm get a delayed roller lock. If it's $1000 to convert the UMP to 9mm then I agree. If the MM kit is ~$500 then it would be worth converting. Your insights are appreciated @Mr.Maim !
 

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Discussion Starter · #5 · (Edited)
Is your USC already converted to UMP spec including the magwell opening in the upper receiver? If so you are good to go for the 9mm conversion. Just drop in the bolt and barrel, and slap in the mag.
Mine is good to go on that font. I was more just looking for opinions and experiences with the kit itself!

I have had two MM 9mm kits: one full auto kit for a post-sample UMP40 and a standard kit for a USC conversion.

MM F/A kit: The full auto kit required some tweaking due to some initial failure to feed issues and after speaking to Mike on the phone about it he asked me to send him the bolt. He performed some vert minor radius adjustments to the front edge where the bolt picks up the round from the magazine and it ran flawlessly for thousands upon thousands of rounds since then. At demo shoots we always provide a list of small arms that clients can sample and oddly the UMP was always choice #1 or #2, only taking second behind an M249 SAW. Demo shoots are high stress: people are paying to be there, and that UMP 9mm never disappointed. I also used the firearm in several subgun competitions and it never failed me there either. We recently sent the UMP along with the MM F/A kit to a new home and I was sad to see it go.

I don't even know if the full auto kit is still available and the amount of people here that could use it are very few. I'm just pointing out with this the fact that if it runs in full auto and does so reliably, you can be sure it'll function in semi-auto. Also, Mike's support of his products is OUTSTANDING.

MM Semi-auto kit: Same experience holds true with my Michael's Machines 9mm USC bolt and barrel kit in semi-auto. I've had this bolt and barrel for 3-4 years now I think. I have never had a single issue with the rifle. Aviator Dave cut the magwell (and barrel slots) and I use a HDPS stock block and a MM 9mm bolt and 7" barrel. This is the range toy that everyone wants to shoot. If I am ammo rich on a particular day I'll let a guest shoot a magazine of my ammo. If I am not, I hand them an empty magazine and tell them to load whatever 9mm they've got with them. It shoots everything including steel case without issue.

Honestly, for as much crap as people give HK for following up the MP5 with the UMP, it is a pretty reliable firearm, and the Michael's Machines 9mm kits keep that reliability going strong!


Thank you! Just the kind of things I was hoping to hear.

So I was thinking about this kind of conversion for my Aviator Dave UMP. I don't see that kit listed anywhere on his website or in his section. The conversion is "just" a new barrel and bolt group right? How much did yours run when you got it? Interested in your perspective because James' thought was that even in 9mm you get that hard recoil impulse of a blowback gun so his opinion was that it's not worth the money to convert to 9mm from .45 in a UMP. Essentially, if you want a soft shooting 9mm get a delayed roller lock. If it's $1000 to convert the UMP to 9mm then I agree. If the MM kit is ~$500 then it would be worth converting. Your insights are appreciated @Mr.Maim !
Regards,
Gai
They are $900
https://www.hkparts.net/shop/pc/9mm-Conversion-Kit-3-Lug-Threaded-HK-UMP-313p2285.htm

I struggled with this for awhile, especially at that price. I only came back to it recently when, for "life" reasons, I had to scale my collection back some. It just makes sense for me to consolidate to fewer calibers, and after all is said and done (I'd sell the .45 pieces) I'd about break even... Still mulling it over.

I imagine its still a jack hammer no matter what caliber its in.
 

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I Bleed Urban Gray
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They are $900
https://www.hkparts.net/shop/pc/9mm-Conversion-Kit-3-Lug-Threaded-HK-UMP-313p2285.htm

I imagine its still a jack hammer no matter what caliber its in.
Right, so are those the MM kits? I'm not jumping into something with a 30% or more markup from HKParts. Can't these be purchased directly from @hk21man ?
The suggestion is that you are correct about the jack hammer in either caliber. Still, I'm with you on caliber consolidation. If colored USP's came in 9mm I would have consolidated on 9mm as well.
 

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The Librarian
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I picked up a UMP 40 parts kits a few years ago at a decent price, sold off the all parts and kept the barrel and carrier for free. I now shoot my oversize pistol caliber SBR in 40 instead of 45. Recoil is significantly better on the follow up shots in 40 than 45.

I can't speak on the MM9UMP kits, but the UMP/USC as a 9mm shooter just sucks in comparisons to other subguns in it's class. Why, oversized mags, oversized gun just to name two. Don't get me wrong, I love my USC/UMP, love it more in 40 than 45, but for 9mm shooting the MP5 is where its at. If I wasn't stuck on it being a HK, the CZ Scorpion, B&T ACP9, SIG MPX would be other options looking into, but not really.

You know who got the 45 to 9mm concept right, Kriss Vector did and it even uses affordable Glock mags.

Give this a look Dan: https://www.youtube.com/watch?v=8-PGW5qVVdY
 

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So I was thinking about this kind of conversion for my Aviator Dave UMP. I don't see that kit listed anywhere on his website or in his section. The conversion is "just" a new barrel and bolt group right? How much did yours run when you got it? Interested in your perspective because James' thought was that even in 9mm you get that hard recoil impulse of a blowback gun so his opinion was that it's not worth the money to convert to 9mm from .45 in a UMP. Essentially, if you want a soft shooting 9mm get a delayed roller lock. If it's $1000 to convert the UMP to 9mm then I agree. If the MM kit is ~$500 then it would be worth converting. Your insights are appreciated @Mr.Maim !
Regards,
Gai
I guess this is one of those things that really falls into "to each his own" to explain it.

...I started to do a PROS v. CONS type list and actually came up with more CONS than PROS so I scratched that. I can really say that everyone that has shot either the UMP or my USC had two comments immediately: "that recoil impulse is weird" and "it shoots nice!". The firearm without the bolt is incredibly lightweight. The reciprocating bolt in such a lightweight frame just feels unusual because we're used to rifles being heavy, or at least more of the overall weight being distributed throughout the rifle which explains the frequent remarks about how it feels when it recoils (I think "jackhammering" is a bit of an overreach :wink:, try a full-auto AK47 THAT is a jackhammer!) so if that is something someone just can't get over then this firearm in any caliber isn't going to be for you. The second comment "it shoots nice" refers to the rest of the rifle. It is a well designed firearm, ergonomically. For me the MP5 is cramped. My nose sits 1/2" behind the rear sight and hits it frequently. Not so with the UMP. The magazine insertion is MUCH better than with an MP5. It points faster and I feel it is easier to be accurate more quickly on shots in the 20-50 yard range. Every time I put an optic on one, I took it off again in favor of the irons (plastics).

I went into my USC conversion knowing that I was spending a fortune on an HK Fanboy's dream and ended up with a nice semiautomatic SBR in the process.

My business went into UMP ownership at the request of several clients as cheap fun guns and they ended up being our most popular demoed firearms by far.


In both cases the money spent was worth it, and I think opened a lot of people's eyes to the USC/UMP because most had heard that they were a piece of crap. One person's opinion regurgitated 10,000 over on the internet.

USC and UMP
 

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I have the USC/UMP in .40 and think it feels the best. Everyone that shoots it absolutely loves it, especially suppressed.
 

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I Bleed Urban Gray
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I didn't like the snappiness of the 40 in a pistol and divested of that caliber. I really do not want to get back into it. I even converted my urban gray USPc to 9mm. @Mr.Maim your insights are helpful. The recoil impulse of the UMP is something that I actually enjoy. Makes you feel like you are shooting a gun. When I shot Jame's SD and a few others' MP5s, they were smooth. Super smooth. Let's you really focus on sight alignment, trigger control and situational awareness. With the UMP (at least in 45) you also add recoil/impulse management to the equation, but I found it addictive and I'm shooting it in semi-auto (the roller locks were all full or burst). I've yet to mount an optic to the UMP. I think conversion to 9mm is just for me to see what the platform feels like in 9. It's a gateway to caliber consolidation too, but that's a fallacy because I'm fortunate enough to own a few colored USPs and don't see myself spending $1000 to convert each one to 9mm with a HK conversion slide.
 

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Discussion Starter · #11 ·
I picked up a UMP 40 parts kits a few years ago at a decent price, sold off the all parts and kept the barrel and carrier for free. I now shoot my oversize pistol caliber SBR in 40 instead of 45. Recoil is significantly better on the follow up shots in 40 than 45.

I can't speak on the MM9UMP kits, but the UMP/USC as a 9mm shooter just sucks in comparisons to other subguns in it's class. Why, oversized mags, oversized gun just to name two. Don't get me wrong, I love my USC/UMP, love it more in 40 than 45, but for 9mm shooting the MP5 is where its at. If I wasn't stuck on it being a HK, the CZ Scorpion, B&T ACP9, SIG MPX would be other options looking into, but not really.

You know who got the 45 to 9mm concept right, Kriss Vector did and it even uses affordable Glock mags.

Give this a look Dan: https://www.youtube.com/watch?v=8-PGW5qVVdY
Thanks for the info. But for me at this point its not about really about whats best. If what I was looking for was a nice, recoil light, 9mm subgun I'd get a Sp5k, register it, and slap on a B&T side folder in a heart beat (the K have always been my favoirte, there is something about the regular guns that I don't like visually). This is about simplifying what I do have. Is the UMP9 the perfect 9mm? Not likely. Would it allow me to keep the looks and line of the UMP that I love (why I spent the money in the first place) and allow me to stop having to stock an extra caliber? Yes.

Still don't know If i'm going to do it. We'll see.

Sometimes I overthink things a little too much :)
 

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Discussion Starter · #13 ·
Right, so are those the MM kits? I'm not jumping into something with a 30% or more markup from HKParts. Can't these be purchased directly from @hk21man ?
The suggestion is that you are correct about the jack hammer in either caliber. Still, I'm with you on caliber consolidation. If colored USP's came in 9mm I would have consolidated on 9mm as well.
When they first came out they where. I do not know if Mike sells them directly. For what its worth, HKparts (at least in the past, this may have changed) was always competitively prices for NON HK factory parts. They definitely markup the factory parts though.


Thanks to everyone for the responses everyone. I'm in the middle of buying a house so I've got time to think about this some more. :biggrin:
 
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