untitled too
I don't know about the airsoft but since you asked about the real guns as well, NO. They are totally different generations and not interchangeable. Assuming you are in the US, getting an UMP (even in semi) would be pretty much impossible. Best thing you could do would be to get a USC and then spend a couple of thousand $ to make it look similar to an UMP. HK hates civilians and won't sell to you unless it is built ugly