The Law Enforcement
Modification or LEM (duh
?) is H & K's
attempt at making a DAO
like trigger for the USP
line of pistols, more accurately a Light Double Action
type of trigger, or ok since you twisted my arm a Glock
ish type of trigger.
DAO guns and the Glock line of autopistols have one important characteristic, which to some people, is also its curse. And that is that the trigger pull is consistent from the first shot to the last. Some say consistently substandard. This is also desirable though as it greatly simplifies teaching personnel (such as LE officers) how to shoot their guns properly. With traditional DA/SA one has to learn how to transition from the first DA shot to the subsequent SA shots.
The LEM was actually manufactured at the request of the USDOJ-INS for their USP 40 compact pistols. It consists of 6 drop in parts that can be installed by any H & K armorer. The basic idea of the mechanism is that it tries to be a DAO but has an internal cocking mechanism which is actuated by the reciprocation of the slide. From the outside it looks like any USP 40C pistol but it shoots like a SA pistol. Only 4000 were made but not all were bought by the USDOJ-INS so some made it to various LE agencies and some even to civilian hands.*
To the privileged few who have actually gotten to shoot a LEM USP, I only hear praise. The reset is also supposedly shorter than that of a Glock so follow up shots can be made faster.
*The LEM doesn't in any way make the USP 40C a deadlier pistol.