Similar to the 9mm C1, the UMP45 is a slow-firing submachine gun with a damage model that leaves something to be desired. It is, however, easy to control thanks to said fire rate and the gentle recoil. The high controllability also allows comfortable use of the Extended Barrel to mitigate damage dropoff.
When performing an empty reload, the bolt magically locks back itself. A more accurate way to model the reload animation would be either having the player to do exactly the same as reloading an MP5 in the game or having the player to press the bolt release after inserting a magazine.