rice said:
there is in fact a 10mm mp5, designed specifically for US law enforcement agencies
The 10mm version of the MP-5 was , in fact, developed for the FBI, back when it looked like they were going to go with the S&W 1076 handgun in (you guessed it) 10mm. This was "post-Miami shootout" (1986 or so) and they did a whole whack of testing to see if they could get something to perform better than the 9x19. To no one's surprise they did, the 180 gr of the 10mm exitting the muzzle at around 1200 fps. They also found that many of the agents did not like the flash, blast and recoil of the 10 to say nothing of the fat that the pistol was big and heavy and many started carrying it in briefcasses and the like. There is no free lunch.
The round was toned down to the tune of about 950 fps (which gave it about the same capabilities as the .45 ACP), however the gun was still huge (well, relatively at least) so S&W teamed up with Winchester, shortened the case so that it would fit into a 9mm-sized frame and. voila, the .40 S&W (one of the greatest modern cartridge success stories) was born.
The 10mm version of the MP-5 was found to be abusive and the guns quickly broke essential parts like locking blocks and that sort of thing. When you can run a 9x19 MP-5 for 3-400.000 rounds with minimal problems but only get 10-20,000 out of the 10mm version, something is wrong. The attenuated version of the 10mm, the 40 S&W had many of the same problems, and in spite of fair sales in the U.S. and Canada, was dropped by HK and is not even supported any longer (to the best of my relatively extensive knowledge). The only MP-5 that HK now makes is in 9x19mm. As it should be.
The FBI now issues the Glock 23 in .40 S&W, and from all reports is very satisfied with it. The FBI is an agency that gets in a lot of shootings, in fact I believe that only the U.S Marshal Service and Texas DPS get in more.
For your information and edification,
Blake ;D