HK USC to UMP Conversion (image courtesy JWT for
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Long, long ago, I watched as a 5th Special Forces Group sergeant boarded a Chinook helicopter in southern Afghanistan. As he walked through the rotor wash and turbine exhaust to the ramp of the helicopter, a young Afghan man emerged from a household alcove with an AK47 and began firing.

He didn’t get many shots off. The SF sergeant, a short man, almost as broad at the shoulders as he was tall, turned from his ascent and fired a snapshot burst from his strange little gun. The rifle’s report made no sound over the helicopter’s noise, and yet the man in the alcove was already lying on the ground. A heavy, 230gr .45ACP slug had torn through his throat.

5th SF Group soldier with UMP45 (image courtesy JWT for

The sergeant looked around, saw me and the rest of my team, pointed to the downed man, got into the helicopter, and flew away.

The shot was a 70+ yard turning snapshot into a partially hidden enemy from a helicopter’s ramp, under fire. It was a shot I would have said was impossible, especially with that rifle. But he proved it wasn’t. That rifle was the Heckler & Koch UMP45.

Fortunately for me and the rest of America — and very unfortunately for the local Taliban — the man I nicknamed “Angry Smurf” would return within a few days with some more team members. They needed another medic and since I was the only one around, I got the job. The job came with a whole lot of range time and some fancy new tools, one of which was a UMP45. Although I never used it on a mission, I got to shoot the hell out of it, and I absolutely fell in love with the little gun.

The UMP40 and UMP45 were specifically built by H&K for the US special operations and law enforcement market, and its had some amount of success there. It is a simpler gun than the MP5 mechanically, and because of its design and materials, it’s cheaper to manufacture.

HK UMP45 (image courtesy Heckler and Koch)

HK’s German engineers essentially took everything they knew about the MP5, and everything they knew about the US market, and built a profitable gun they thought their customers would want. They were right.

Unfortunately, a host of laws make it difficult for H&K to legally import the UMP guns, even with just a safe/single fire trigger pack. Each and every one of them is an NFA item. Even though Heckler & Koch refer to it as the Universal Machine Pistol, the US clearly defines them as short barreled rifles, and thus subject to all the NFA rules.

HK UMP45 right side (image courtesy Heckler and Koch)

Because of this, as well as what I’ve always found to be an underestimation of the H&K market in the US, ze Germans do not sell the UMP here in any variety, except to military and law enforcement units. Instead, they capitalize on the zeal for their products with the Universal Serial Carbine, a full 16” barreled, fix stock version of the SBR.

HK USC left side (image courtesy Heckler and Koch)

But that is not the UMP. Which is what people actually want.

In fact, people want them so much that they’re willing to buy the USC just to scrap half of it so that they can legally turn it into a UMP. And if you want to own a legal UMP in the US, that’s exactly what you’ll have to do.

USC to UMP45 Conversion (image courtesy JWT for

There are few different way to skin the conversion cat. Just search “USC to UMP conversion”. It’s definitely more involved than simply swapping out the barrel on an AR. You can either pay someone to do it for you or you can tackle the job yourself. You’ll find plenty of resources on the internet and you’ll find a few different options on which way to go about it.

No matter how you do it, this is not a cheap process, even if you choose to do it yourself. Either way, first, you’re going to have to waste a lot of money buying that USC.

The upper receiver is the serialized part of the gun, so yay, you get to keep that bit. But not everything inside of it.

USC to UMP45 Conversion parts (image courtesy JWT for

Of course, for the UMP, you’ll need to order a new pistol-length barrel. Before you order your barrel, you’ll need to put in an ATF Form 1 and request permission, to make sure it pleases the king that you’ll be converting this rifle into a short barreled rifle. That request, of course, comes with the obligatory $200 tax stamp.

You’ll need a new lower ($300-$400), barrel ($200-$250), and stock block ($250-$300). That’s before you do any kind of rear section fusing, or any dyeing of the polymer, or any of your vent cuts or milling. The difference between doing it yourself and paying someone else to do it is about $350, so all in all, plan on spending $2,000 to $2,500 for what is very much a semiautomatic UMP45.

You’ll also need to be careful with 922R compliance, although it’s pretty easy to get to compliant, as a US-made magazine alone is three parts and there are now many compatible parts made here.

USC to UMP45 Conversion folded (image courtesy JWT for

Is it worth it? For some people, clearly. Most companies that sell the USC/UMP conversion or provide conversion services are sold out or have a waiting list.

Given the cost and the hassle, why is this such a popular build? Is it just HK fanboi-ism or something else?

For me, it was a little bit of both. I’m not actually much of an HK fan. I’m a huge G3/PTR91 fan and I’m an MP5 fan. Beyond that, their modern guns don’t really do much for me.

That is, except for the UMP45, which I find to be one of the most comfortable, shootable, practical firearms made in the last 50 years.

USC to UMP45 (image courtesy JWT for

Fortunately, I found a guy that needed a little bit of money more than he needed the gun and I was able to buy it from him for about half of what I would pay new (and that included the suppressor). Of course, I also had to ask permission for the Form 4 SBR transfer, as well as for the suppressor, pay another $400 in stamps, and wait 11 months to get the ATF’s OK. So I dropped almost half again the amount I paid for the gun to our federal overlords (in all of their benevolent wisdom.)

But this is a shooter’s gun. It can be well argued that the AR pattern rifle was the culmination of everything we knew about individual gunfighting by the 1950s. If that’s the case, the UMP series is the culmination of everything NATO knew about individual gunfighting in the 1980s.

USC to UMP45 Conversion trigger (image courtesy JWT for

There are a total of four separate trigger packs available on the UMP45. That includes the 0-1 Trigger group, which is the purely safe and single fire option available right from the factory. So if you want a “real UMP” know that doesn’t actually have to mean select fire.

In fact, the only way I ever saw it used in combat was in single fire or two-round burst fire. That’s because, unlike the MP5, the UMP isn’t a roller lock firearm. That’s right, if you, like me, appreciate the stretched out recoil impulse and feel of the roller lock mechanism, you’ll despair because the UMP doesn’t feel the same. I’ve fired the UMP45 in full auto plenty of times, and keeping the gun tight on target at 700RPM is difficult. That’s one of the big reasons that Special Operations personnel generally kept it to single fire or two-round burst fire.

The trigger on the UMP is a very German “meh”. I say a German “meh” because although it has very little squishiness, it’s also quite heavy at 9 lbs. Given the gun’s basic design, and that so many of the trigger parts are plastic, there’s really not much to do about it.

I’ve heard of people bringing the weight down a pound or so, but that’s about the extent of it. The reset is fairly short and you can definitely feel it. Even with the weight, the lack of grit or slop in the trigger, combined with a short reset mean that you can still get rounds out in single fire quickly and accurately. I would love someone to come up with an alternate trigger mechanism for this gun, something in the three-pound range. I just don’t know how they would do it.

USC to UMP45 Conversion right side (image courtesy JWT for

The safety/selector lever as well as the magazine release are both ambidextrous and easy enough for a man with size large hands to reach. For those of you with tiny hands, it’s going to be a stretch.

If you already own an Accuracy International Rifle, and yet somehow need even more plastic in your life, the UMP is for you! With so much plastic, and such light weight, you’d think this gun would bash itself apart.

To the contrary, there seems to be little long term wear on the gun at all, despite running tens of thousands of rounds through it. Agencies that use the UMP40 consistently record less service required on them than the MP540.

USC to UMP45 Bolt (image courtesy JWT for

That has to be partially due to the massive bolt HK uses in the UMP45. Really, this thing is a Teutonic tectonic plate moving back and forth inside the upper receiver. Moving all that mass helps to diminish some of the felt recoil of the gun and keeps the muzzle down. Plus, if you ever run out of ammo, you can use the bolt to bludgeon your opponent into submission.

USC to UMP45 front sight (image courtesy JWT for

The front sight is, again, all plastic. It’s a simple flat black triangular blade protected by the also-plastic loop. The rear sight is elevation and windage adjustable with a hex key, and has a standard-bladed notch or a flip up fairly wide aperture sight. The blade is better for accuracy work, but nothing beats that aperture for fast work, especially in low light.

The rifle is built to accept a Picantinny rail on top, as well as 180 degrees more around the fore end of the gun. You can find these rails of varying quality on the internet from $19 for plastic or $75 for genuine HK rails, and a whole lot in between.

USC to UMP45 Conversion rear sight (image courtesy JWT for

A red dot/reflex optic on top of this rifle is what makes sense, and it’s the only way I’ve seen it actually deployed. That’s not because the irons don’t work well enough, they do. But much of the work these guns were designed to do happens in the dark, and even though you can get replacement tritium sights for the gun, the red dot optic excels at low light shooting, especially one that is NV compatible.

USC to UMP45 Conversion paddle release (image courtesy JWT for

Unlike its older sisters, the UMP locks back on an empty magazine, slightly decreasing the reload time. The paddle style release in front of the trigger guard is easy to find without your eyes focused on it, and the proprietary magazines drop fast and easy. For my fellow AK enthusiasts, no, you cannot slap out the magazine by hitting the paddle with a fresh mag and knocking the old one out. The magazines are set too deeply in the receiver for that. I know, I’m sorry too.

USC to UMP45 Conversion bolt release (image courtesy JWT for

There are two ways to release the bolt on the UMP. First, there’s simple bolt release button on the left side of the gun. Fast and easy. You can also reach up and pull back and release the charging handle, which is slower and more likely to cause an error, but it’s way cooler.

USC to UMP45 Conversion charging handle (image courtesy JWT for

If you want to stay true to the original HK, you’ll need to get an HK flanged style barrel. The H&K UMP Armorer’s Manual proudly proclaims that HK “selects the finest French steel for its barrels” and then hammer forges and chrome lines them in Germany. That’s all cool, but it will dramatically limit your options as far as muzzle devices and silencers.

USC to UMP45 silencer (image courtesy JWT for

For this particular conversion, the builder chose to go with an American-made barrel of American-made steel, and a one-off custom silencer from Gemtech. According to the Gemtech manual, “the entire suppressor is constructed of high tensile strength aluminum alloys”.

This is the same Gemtech suppressor specifically built for the UMP45, but without the Posi-Lock detach for the UMP, and instead using a more traditional direct thread attachment. It has never loosened during firing, and is extremely difficult to twist off every time I clean the rifle. As I said, it took another $200 and an 11-month wait to get this can approved, and I’ve never actually shot the gun without the silencer attached. I have no plans to, either.

USC to UMP45 Conversion folding stock (image courtesy JWT for

An obvious big difference between the parent USC and the USC/UMP conversion is the folding stock. This is what takes the most work for the conversion to look and feel like the HK-made UMP, and it’s worth it to get it done right.

Most sub machine guns, and even a whole lot of the newer personal defense weapons, seem overly cramped, putting the shooter in awkward positions. That’s OK if you’re just shooting a bit, but it makes practice and drills uncomfortable as well.

USC to UMP45 Conversion stock (image courtesy JWT for

The UMP, on the other hand, feels just great. The balance of the gun, with the suppressor attached, is perfect. Nothing is cramped, everything is where it should be. The weight is right in your hands, not in front of them. The stock geometry fits the shoulder, snapping quickly up and locking in tight. The stock doesn’t look like it would fit so well, and handle recoil so well, but for anyone that shoulders this rifle, feeling is believing.

In the highly unlikely case of a malfunction, the charging handle is right above your support hand, for righties. It’s nothing just to pick your hand up, pull and lock back the bolt, strip the magazine and fix your problem to get the in back in the fight.

Off the bench the UMP is OK. From the kneel, the UMP is also just OK. Standing and shooting in rapid fire, though, the UMP is great.

USC to UMP45 Conversion fast groups (image courtesy JWT for

At The Range At Austin, I pushed a target out to 25 yards, and waited for my timer to go off. When it did, I snapped the gun up, emptied a 25-round magazine, did a mag swap with the 10-round mag and emptied that one too. I did that three times and averaged 12:11 seconds. In my worst of the three groups, I had five rounds outside of the 8-inch circle of the target, and they were really close.

But it’s walking while shooting at a moving target that the UMP45 shines. Because of the stock geometry, as well as the weight and balance of the gun, the USC/UMP conversion absolutely floats while you move. It’s nothing to keep the gun on target while aggressing, or moving laterally. Target transitions are fast, and you can maintain a good view of the field in front of you while you keep the gun up.

USC to UMP45 Conversion 100 yard groups (image courtesy JWT for

This isn’t a sniper rifle. Heck, according to the Germans, it’s not even a rifle. Still, given its fairly short sight radius, it achieves admirable precision.

At 100 yards in a Caldwell Stinger Shooting rest, the 200gr Freedom Munitions hollow point round gave me a 4.5-inch average five shot group for four rounds. At the 50 yard mark, which is the much more likely longest range the UMP was designed to operate in, the 230gr Sig Sauer FMJ printed 2-inch groups, as did the new Remington 230Gr Black Belt Golden Saber Round.

That level of accuracy off the bench translates to solid T-Zone shots on the move for close in-aggressive shooting. Of course, that’s what the gun was made for in the first place, and where it absolutely shines.

HK Operators Manual "clean is clean" (image courtesy JWT for

As of yet, I have found no reasonable upper limit on the reliability of this firearm. Despite the directions in the Armorer’s Manual, I regularly put 2,000 rounds through it at a time without any maintenance at all. It barely even needs to be lubed. In fact, I think the silencer needs cleaning more than the rifle itself does.

I’ve run hollow points, lead SWCs, flat point round nosed bullets and standard FMJs through the gun, even mixed in the same magazine, without any issues what so ever. The USC/UMP retains every bit of the supreme reliability the UMP is well known for.

The USC/UMP45 conversion feels exactly like the issued UMP45 I shot in Afghanistan. It’s unfailingly reliable, and accurate.  It’s also a gunfighter’s gun.  Fast to the target, fast in transition, natural and intuitive.  The conversion didn’t disappoint one bit, and I’m lucky to have found a good deal on one.

Now, the real question is, with HK USA a thing now, and with the demand for this gun obviously there, why doesn’t HK start producing these guns here in the US and make them available to the public? After all, there is a fight going for which company’s PCC or sub gun can claim the title of “MP5 Killer.” You’d think that would be HK.

USC to UMP45 Conversion ride or die (image courtesy JWT for

USC to UMP45 Conversion (It’s a UMP45)
Caliber: .45ACP
Length: 17.91″
Width: 2.72″
Height: 12.87″ (with 25 round magazine)
Barrel Length: 7.87″
Overall Length: 17.7″ stock folded, 27.1″ open
Weight: 5.06lbs
Price: $2,000-$2,500 (plus $700 for suppressor)

Ratings (out of five stars):

Style and Appearance * * * 
All industrial, all the time. At least the plastic doesn’t look like cheap plastic. You like black? Because it comes in black.

Customization * * * * *
This is already a highly altered firearm, and if you want, you can alter it a whole lot more. There are multiple stocks, barrels, sights, etc. Only the AR pattern rifle is more customizable.

Reliability * * * * *
Truly exceptional. The thing runs any round, including multiple types, brands, starting loads and +P alike. It needs to be cleaned, probably.

Accuracy * * * * *
Four-inch groups at 100 yards and multiple rounds deliver 2-inch groups at 50 yards, with the factory “irons.” Exceptional.

Overall * * * * *
This is a purpose-built gun, and it fulfills that purpose completely. It’s a room clearing machine, and for any human target under 100 yards, it’s completely capable. It runs forever and will shoot an eye out at half a football field away. It’s just an absolute shame that building or buying this rifle costs so much, At over $2000 ($3000 with the suppressor), I’d likely pass on the gun. But if you can get lucky with a deal, or if a UMP45 is worth the cash to you, the USC/UMP conversion shoots, and feels exactly like the UMP straight from the Bundesrepublik.

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  1. Unlike its older sisters, the UMP locks back on an empty magazine, slightly increasing the reload time.
    Do you mean it doesn’t lock back? I don’t know the UMP, but your context (and lack of mention of the HK slap) leads me to ask.

    • It should say “slightly decreasing”.
      Yes, it does lock back, unlike its older sisters, the MP5.
      There is no HK slap on a reload with the UMP, only on the initial load from a locked bolt position, or possibly to clear a malfunction. The bolt is locked back and released in one of the two ways mentioned in the article.

        • You can ‘HK slap’ it. The charging handle works exactly like an MP5, in every way. The issue is that it also has an AR style last round bolt hold open… so if you run your mag dry, and it locks back, your charging handle is in the forward position, and there is nothing to slap.

          If you lock the bolt to the rear using the charging handle, and load a magazine, you can slap until your hearts content, and it will work exactly as it does on the MP5.

  2. We’ll revisit this review when that Georgia factory starts spitting them out, along side some new 4.6×30’s.

    • This article, along with the re-release of the USC, was partially written in the hopes to encourage precisely that action on the part of HK.

      • I would mortgage everything I own if I could walk out of a shop with an MP7. Granted, I would prefer it to have a 2-shot burst, and along with that, a Kriss with 2-shot burst, or the above mentioned with 2-shot.

        • I don’t know what your net worth is, but that can be done entirely legally. It’s going to take about $7k, plus the cost of the firearm, and a (preferably local) law enforcement entity that is willing to write you a letter that they are interested in testing and evaluating it.
          It will belong to the FFL you would have to create, and not yourself. It would not be transferable, but it can be done.

  3. Thanks for the article. If HK releases the UMP45 as a pistol with the means to mount a stock and does away with the silly ten round single stack magazines I will be first in line to buy one.

  4. Thanks for posting the in-depth review! Prior to HK bringing back the mp5 with the SP5k, a USC conversion was the only way to get a German made, brand new HK “sub gun.” The USC pistol grip is quite large and doesn’t fit my hand like the UMP grip. If they could bring it in as a pistol with the UMP rear end/stock mount rather than the USC’s open hole the conversion would be easy and much more accurate. Basically like the B&T APC 45. The APC 45 is probably a better deal if you want to have a gun like this, ready to go out of the case. But if it needs to say HK, then this is the one. Plus it has a non reciprocating charging handle, and you can swap calibers by punching out a barrel pin and dropping in a different bolt/mag. For a price. It is big though! Really long. I like it though!

    • You bring up another good point about the gun. Caliber swaps are easy, but certainly not cheap. The upside is that you can run .40SW+P all day long in it once you do that swap.
      Or, of course, you could just build it as a 40 instead of a 45 to start with, but it’s not as quiet at the .45.

  5. “Before you order your barrel, you’ll need to put in an ATF Form 1 and request permission, to make sure it pleases the king that you’ll be converting this rifleinto a short barreled rifle. That request, of course, comes with the obligatory $200 tax stamp.”
    “You’ll also need to be careful with 922R compliance..”
    ” Of course, I also had to ask permission for the Form 4 SBR transfer, as well as for the suppressor, pay another $400 in stamps, and wait 11 months to get the ATF’s OK. So I dropped almost half again the amount I paid for the gun to our federal overlords..”
    Just readin these three sections of the article is enough to make one want to vomit.
    When are we going to decide enough is enough and use our second amendment and arms for what they were intended? Hey JWT, nice to see a well written and informed article without a hundered errors here for a change. TTAG is starting to hurt in these new hands.

    • 922R also only applies if you’re importing. Once it’s in the states anything is fair game.

      • Just to be clear, 922 still applies once the firearm is in the US. Eric only means that 922 compliance is not a thing if it is manufactured in the US. Since the HK UMP only needs 3 parts to be in compliance, and a US manufactured magazine is 3 parts, well, there you have it. You could have an all HK firearm, with only the magazines being made in the US and still be in compliance. But you’d have to stick with the flanged barrel, which is a no-go for me.

        • Eric in Oregon,
          For an individual, I have no idea when, or even if they are ever checked. I’m an FFL/SOT, so I get checked and the occasional ATF audit is quite detailed.
          The fine for non-compliance is ridiculous, like $250k or something insane.

        • Thanks for the info, after my original post I looked it up and my understanding of 922r was … incomplete.

      • If 922r was enforced most SKS rifles at gun shows would be confiscated. No cop is going to know what is US made on a weapon. I believe there has only been one successful 922r conviction.

    • Neat guns. They did not review very well here at TTAG. I’ve seen them have tons of reliability problems for the ones they rent at The Range at Austin. I have never personally had any issues with them, and I suspect the reliability issues are magazine related. I’ve always been a fan.

      • I shot a Kriss at a range in Salt Lake City, and fired it full auto. The guy doing the rental said the same thing – they have reliability problems with them and have to constantly clean them.
        One of the mags simply dropped out while I was shooting it full auto.

        And I would love to own a UMP.


      • The insides of the Kris reminds me of the old Borchardt pistol. The Borchardt wasn’t a success until a guy named Luger reworked it.

    • Yes, tens of thousands, all suppressed. I clean it by putting the whole thing in the Hornady Hot Tub and then swabbing the barrel. That’s it.

      • When you say, “whole thing,” you mean the whole thing, as in, the entire gun? Not just the metal, but, also the plastic? I’m just asking because I’ve wanted to get a Hornady hot tub. Is it dangerous to the polymer or does that get nice and clean like the metal components?

      • I’ll stick with the stock gun with 20rd mags. I just feel these conversions are for tactical fanboys who don’t want to sign on the line or apply at an Agency. They would rather buy their way in and not put in the blood,sweat and pain. You were smart to get one used. The bad part is you won’t have HK support if needed.

        Great review! thanks for writing it.

    • By every objective measure, yes. But the Camp Carbine is a great little gun, with some real American tradition behind it. It was a shame to see it discontinued.

    • In my experience, the “magic” doesn’t really happen until about the 23mm size range. Because at that range, people just disappear.

  6. I’m posting here because military units clearly do not use weapons in the .45acp caliber.

  7. Did this conversion with a rear stub fuse, had Tom at tommybuilt tactical do the fuse. He does great work and fast turn around. Love the gun, wanted to do a SL8/G36C conversion as well. Just not looking forward to the 4-5k I’m going to drop to do it though. But thats the price of having hecklerandkochitus. Lol

    • The G36 was a failure as a battle rifle. Bundeswher is going to the 416.
      I wouldn’t spend that kind of money to have a hacker carve up a perfectly fine weapon.

      • Nothing says poser like a fake gun. Same with people who spend big money to make a high end “replica” Rolex. The money spent making a poser gun could be used for real training.
        Tac fanboys will just buy their way in, sigh.

  8. Man…its a good thing you did this review and not Leghorn.

    If it were him he would suggest making a bunch of illegal changes to the gun, not tell you its illegal, then go on to praise a gun only later to say it sucks and give it 1 or 2 stars or vise versa.

    He need to really focus on his knowledge of firearms in general and the laws and regulations of firearms in this country before he writes another review for your site. He’d be much better off doing that instead of trying to get as many one line zingers in his articles to make himself look like some sort of comedian. Seriously thou, show that guy the door…

    Oh and lastly. The UMP sucks. Dont need to read a review to understand this. And anyone moronic enough to spend a shit load of money to upgrade a design that might be the worst HK has ever produced (exception. the G36) and for it to have no real practicality in 2018 (either use a 9mm suppressed SMG or use an SBR) deserves what he gets when he’s all done spending shitloads of cash on a sub par platform. Its big and bulky, far to light for how big it is, has possibly the worst trigger of any HK design and has a bolt that you can feel slamming the rear of the receiver on every shot. Did i get it all? It was suppose to “replace” the MP5. Funny cause it didnt and wont ever. You might be the only person on earth who has experience with this platform to give it 5 stars. you must be going off a 10 point scale. If thats the case then your dead on.

  9. I love your writing on H & K 45 . I have been looking for a 45 carbine for when I go to my shack in the woods . I had a close encounter with 2 wild dogs I was lucky I had my 45 pistol . I have since been looking around for a carbine in 45 because I’m no great handgun shot I prefer a rifle or carbine . Great article.

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