once in a while, i have seen performance reports on the net from various police dept. as to either guns or ammunition, primarily involving financial and acquisition issues, not particularly up to date reports.
when in doubt, ask a police officer friend, they are trained to remember their ammo types, ballistics and terminal effects
the general rule for a while was that if you have friends in municipal police, go with a 40 cal, if you can use some of their ammo at the range, and if it was the rcmp, then the 9mm handgun would be the choice to have with you
my own opinion has been not to follow the police usage, because it has more to do with budget than performance on the streets and what actual officers would rather have.
through the 80's, it has been civilian shooters who advanced the use of 45 and semi-autos when our police forces were stuck with 38 special revolvers (budgets and the lowest common denominator approach), and as well, involved with IPSC while police departmental competitions were kept to ppc shooting.
as for ammo, i think we have more access to purchase and use high performance exotic ammo than police issued. imho
