Instead, enthusiasts follow a well-traveled path of converting a legal civilian carbine into a faithful UMP clone. 1. The Foundation: The HK USC
To turn that USC into a 9mm UMP, you must perform a caliber and furniture conversion. H&K USC: Civilian Version of the UMP Submachine Gun
: The USC is typically chambered in .45 ACP and comes with a 16-inch barrel and a fixed thumbhole stock to meet import regulations.
The journey begins with the (Universal Self-loading Carbine), which is the factory-legal civilian version of the UMP.