So today at the IDPA Pistol Caliber Carbine day, one of the folks who brought stuff out we don't normally see was the Chief of [a local agency] that still has .40 UMPs in the arms room. He hates them, but it's all he's got so he brought it. And... let some of us shoot it. So, now I have a mag of shooting and moving with a UMP!
Chief Steve hates it. HAAATES it. Big, heavy, horrid recoil. On shooting it, and then immediately shooting my "Colt" carbine, tend to agree with at least the recoil. It kicks far more than it has any right to. Not sure why. He says: giant bolt.
Otherwise, a fine successor to the MP5. Trigger group seems identical, charging handle is so similar that I thought it was the same, but the distance is a bit different so I missed going to slap it down the first time. Mag latch is different but similar enough as well you make do, etc.
I had the same experience with the HK trigger group I always do, which is fine. I have, even with my deformed thumb, no issue using the fire selector. Everyone else complained like always, did stuff like put their thumb on the other side to run it, etc. Trigger itself was fine, smooth, adequate weight.
I did of course slip once and purely accidentally knocked the selector from semi to full for one target. You aren't allowed to go full auto for IDPA. "Whoops." But, not much less controllable than a full auto AR (5.56 - never done a full auto 9mm), trigger helps a lot with that, so easy to press-release and get three nicely grouped shots. With any practice, I am sure I could do two. Though, it also had a 2-shot burst setting, so if mine personally, I likely would just leave it there all the time.
LOP is a bit long, and the stock is too rigid, sorta made my cheek tired by the end of my very short run. I might be happier with an RDS (it was irons only) to get my head higher, else it's getting covered in sticky neoprene sheet like my FAL Para, again: if I owned one. Or, I bet B+T makes an awesome aftermarket stock as that is their way.
Mags are HUGE. Couldn't even sorta stick in any pouch I own, ended up in my back pocket. And a bit hard to handle generally. Translucent is damned nice, but too smooth. Like an AUG or SIG without the reinforcing grooves. Some modern translucents, maybe Turkish HK33 and... (New) Skorpion mags (?) have tiny raised bits that give more purchase, help a lot. Fat floorplates are also weird, stupid to me. Wonder if you could stretch a 9mm old-school magpul onto one?