Brought to our shores originally for the FBI. These were NICE subguns...but with the "availability" of several different loads made for the FBI 10mm, they had cycling issues with different types of ammo. Thus the "fix" were three different locking pieces, engraved one marked 26 was pretty rare and HK substituted the 90 deg "LO 24" marked piece. The other was marked "HI 25."
I worked on several of them back in the day. Raleigh PD had some and so did NC Central Prison system. Some of them I worked on had used the wrong ammo with the wrong locking piece which caused them to over cycle and produced a "dent" at the back of the receiver that when it got big enough would cause a stoppage. Fairly simple one time fix. But, the different ammo specs over time seemed to cause more problems than they were worth. And I think Raleigh went to .45 caliber and traded in all their 10mm weapons. I don't remember where they went, I was hoping to get some or all of them at the time. Same with the FBI weapons. I was told that (like too many other tax payer supplied) Govt weapons they were all destroyed except for a couple of museum pieces.
Like to original post says with the correct ammo and locking pieces they were the cat's meow for subguns!!!
I did run across a half dozen .40s a few years ago...some, maybe all, became 10mm conversions. Haven't seen or heard of either now for some time.