Introduced two decades ago as the consumer variant of Heckler and Koch's latest sub-gun goodness, the HK USC has been available off and on-- mostly off-- since then.
Ah, the UMP
Designed in the late 1990s as a more updated offering for those who liked the company's vaunted MP5 series, the Universal Machine Pistol, or UMP, was a select-fire submachine gun that incorporated lots of polymer to both simplify production and help make the gun as light and compact as possible.
The UMP was cool, and, hitting the market in 2000, soon landed some military and LE customers.
Then came the USC
While the UMP was unveiled, a semi-auto version derived from it was pitched to the market by HK as a "civilian utility carbine." Dubbed the Universal Self-loading Carbine, or USC, it had the misfortune of coming to market smack dab in the middle of the now-expired Federal Assault Weapon ban and thus had to be imported with a fixed skeletonized buttstock, 10 round single-stack magazines, and a 16-inch barrel. It was only imported in .45ACP.
The USC has some good traits, such as an oversized trigger guard for easy operation while wearing gloves, a cold-hammer-forged target barrel with a reputation for being accurate, fully adjustable rear diopter sights, reliable action, and a tough polymer construction that is corrosion-proof. On the downside, it runs 35.4-inches overall and weighs slightly over 6-pounds while having the same magazine capacity as a Hi-Point 4595 carbine.
However, there are lots of shops that specialize in doing UMP-ish conversions of stock USCs which gives one the option of a more high-speed German .45-caliber PCC akin to LWRC's SMG 45 (which often costs about twice as much as a stock USC).
For those satisfied with the original layout, HKs rarely if ever lose their value if kept in very good condition. Speaking of which, the USC has only been imported in a few, short, spurts over its limited production, making the likelihood of ever bumping into two of them at the same time low. Prior to 2018 when the latest crop started to trickle in, they were only imported between 2000-2003 and 2007-2011. With that kind of track record, it is about time for HK to shut the door on the USC again, after which, prices will spike from today's mildly expensive to tomorrow's man-I-remember-when-those-things-cost-half-that-much.