If I remeber correctly, when everyone was making a mad dash for the 9mm, the FBI wanted something a bit more substantial. The 38 special and 357 mag are all right, but one gets tired of the flash and recoil in a wheel gun.
In a sense the 40 was a good idea ... nominal 135 grain that could be pushed I think to 160. It gave a bit more confidene in knock down power compared to the 9mm, but still kept the benefit of being lightweight and larger capacity magazines.
The drawback .. unless something has changed, the 40 has the notoriety for weak cartridges and relatively high pressures ...the bottom portion is not adeqately supported by some handguns, particularly glock. Makes for a nasty surprise, oftimes blowing the magazine out of the gun and somtimes worse. I don’t ever recall anyone being injured though.
All of that for another gubmint agency ... It isn’t a shock that the 45 acp is the round everybody seems to return to. Stopping power that is never questioned. Reliabiltiy .. unmatched. Availability .... well until recently .. sigh ...
A lot of ccw’s carry the 9mm for size and high number of rounds. I stick with the 45 and now carry a Sig p220 elite. Perfect sized and weight and ultra reliability without sacrficing rounds (8 + 1) If I need more than that, Oh well .. I hate carrying a spare magazine. It ‘s why I spend time on the range. 1 to knock down, 2 for insuance. I believe in efficiency.
Case blow out is all Glock
That wont happen in CZ or Sig or SW
They chose to open up the ramp for reliability of feeding, but that sucks when a case ruptures and blows the mag out.
Ive seen it happen twice.