Thank you, Sig_Fiend! I saw an H&K UMP 45 for the first time a couple of weeks ago, and fell in lust. Been dreaming about owning one since, but didn't think it was possible - even in semi - so never did the research. Now all I have to do, after finding one at a non-ridiculous price (which may not be possible), is do the homework and file the appropriate paperwork (not in that order, clearly). Can't think of a better home defense/zombie killer. You made my day!
All UMPs in civilian hands are semi-auto and started life as USC Carbines. The carbines you can pick up from HK for under $2K, and then convert them with UMP parts from HK. Be aware of 922r compliance though.