No.
I've done a USC-UMP conversion, so I've done this all before
In order to get UMP magazines to work in a USC rifle, you need several parts and to do a couple things:
- get UMP45 lower/trigger group
- Get conversion stock block, and stock
- install USC45 trigger parts in UMP group
- cut mag-cutout area in the USC45 UPPER so that the magazines feed lips can fit into the upper properly
That is the most basic version of it. You're looking at spending anywhere from 500-900 bucks on the UMP lower depending on how lucky you are, 3-400 on the stock block, another 150-300 for the stock (depending on what type of rifle stock you want) and THEN for mags, who knows with how expensive they are in the states.
Member here chkam got me a lot of my stuff, but the parts don't come cheap at all.
A MUCH better bet is to see if you can get ahold of the HERA Arms stock kit (5-600 bucks for a folding pistol grip stock that uses the USC single stack lower) and the HERA 5/20 round magazines, they are a longer single stack mag.
However for what its worth, they are incredible carbines!