Greetings all. Approaching the omnipotent knowledge base, please tell me about these rifles. No specific reason, just an inquiry.

What do you want to know?

I have a grease gun mag converted USC from the Way back.

-very accurate
-makes a sort of Thud on firing that is fun and satisfying.
-PITA to clean, at least like I like to clean. It’s not about the need for a tool to tear down but the fact that cleaning out that upper and chamber is a bit of a pain.
-the above said.......it will run DIRTY like Dirty as all get out, like dirty porn girl dirty.
-the Grease gun mags can be a tad finnicky in mine. Loading the first round REQUIRES THE “HK Slap” and some mags need to be downloaded a round or two but actual shooting function is great. (Again mine is a conversion.)
-Rails up front are SHARP. Get rail covers.
—All in all its super fun but ain’t no MP5.

I had one a long time ago. Mine was one of the first 200 IIRC, so early that it needed the charging handle recall--the very early ones had plastic shanks so when you did the HK Slap, you could inadvertently break the handle off (bad news because you just chambered a round and the only way to unload the gun would be to either disassemble it or fire it).

It's a neutered UMP, which isn't a very elegant gun in its fully-featured state. If you want to know what one feels like to shoot, put a brick in a shoe box and shake the shoe box back and forth.

Accurate, and light for a .45. It's limited by its factory magazine capacity and receiver configuration. The pistol grip is very big and the trigger isn't "match" by any stretch of the imagination.

There are better PCCs on the market today.

If its HK-ness that you want, I would stick with the MP5 clones--RLDBB system is much more elegant than the UMP/USC's blowback operating system and far better behaved under rapid fire.

If you have the money and are interested in a modernized and not gelded USC, take a look at LWRC's SMG .45. The SMG .45 combines the best parts of the UMP with ergonomics and control points of an AR. If I had to get a .45 SMG/PCC LWRC's SMG .45 is really the only one I'd be looking at.

My interest is as a newbie to the gun. Simple curiosity. Thanks for this feedback.

I have two of them in the safe. Little to no recoil, easy to put everything in one hole. The popular conversion is the UMC conversion to get rid of the thumbhole stock, though parts have gotten harder to get and you don't hear about them much now.

The full auto versions are fun (UMC).

Note that the UMC conversion for the USC doesn't make it full auto (illegal); it just makes the USC look like a UMC with a new lower, shoulder stock, etc...and a lot of owners SBR the carbine. It also takes replacing a number of HK parts with US made parts, to stay legal.

The USC is fine as is, albeit with a small mag capacity, and expensive magazines. It's bulky for a 10 round carbine. It's also quite light.

I have an early gray USC that I converted to a UMP carbine (kept the 16“ barrel). The main issue with the USC that I saw was the limited 10 round mag capacity. Hera makes 20 round single stack mags that work in the unmodified USC, but they are pretty expensive. IMHO, it’s not worth it unless you modify it to take the 25 round UMP mags, which adds cost.

I shot one with a can on it in 2013. Blew my mind. It's a serious weapon that can deliver 30 rounds or whatever of 45 into the head of a silhouette at 25 yards with ease, had a red dot on it. I was not shooting slow and it was just effortless. It changed my thinking about sub guns as I like 45. Great round to suppress and just a big slow slug smashing into things.

I still want a 45 subgun but not the HK. The LWRC looks awesome, B&T too. They are just so expensive it'll probably never happen for me.

Gets me excited though.

I had a phase about these and have several, a couple stock and one that went the UMP conversion route. Its a design to meet a legal rule and other than its an HK its not very interesting today. I'm not sure where cslinger is going on cleaning since I'm pretty convinced you could shoot it forever without cleaning and it would still run. Parts are a challenge, but not likely needed. Mags are limited unless you do something to the gun and expensive.

Have a early one, dyed it black. Used it for carbine plate shoots. It was deadly accurate. And the 45 hits so hard out of a 16" barrel, it would break welded plates reguarly.

I was able to chrono some +P rounds out of it one day. Had some breaking over 1220 fps, forgot if 200 or 230 grain. It was hitting as hard as a 44 magnum.

I believe Tommy Bostick used to do stock conversions to the thumb hole stock to make it a true pistol grip with a fixed stock.
He worked magic with a hot knife and a heat gun.

He still does if you want one converted to a ump clone. Not cheap but very well done.

The (unconverted USC is ok) but not real fun. It only has 10 round mags and an ugly ass thumb hole stock.

The converted USC (to look like an UMP) is much better and has 25 round mags. I now own 2 of them and it's my favorite rifle. I have 1 old, 1 new. The older one was from before they were discontinued, the newer one is from the new run HK did 2 years ago.

My 1st one I will leave with the 16" barrel, the 2nd one I am saving up to have cut, crowned and threaded to have a suppressor put on.

To have one converted is a little pricey but worth it IMO. My 1st conversion was done locally by a "HK gunsmith" who took 5 months to do it. After all was said and done, he did a nice job but way too many excuses soured me on him.

My 2nd one was done by Black Ops Defense http://blackopsdefense.com out of Harrisburg, PA. The owner was awesome to work with. I actually drove to his house and dropped my rifle off and talked with him for about 20 minutes. He does the billing side from his house but has an office where the actual work is done. I have nothing but good things to say about them.

See if you can find a MMUMP from Michael's Machines, those are made from original UMP receiver sections that are very carefully demilled and re-welded back to semi only guns. Probably the most authentic UMP clones short of getting a real one.