I posted this reply in another thread, and I think it's applicable here:
I started as a LEO in 1977; at the first department, we had to buy our own guns and carry the department issue ammo. Guns had to be Colt, S&W, or Browning, in 9mm, .38 Special or .357 Magnum. All issue ammo was Remington; 115 grain SJHP for 9mm, 125 grain SJHP in .38 Special. Most of the guys carried a K-frame revolver, either a 19/66, two guys carried Colts, and the 9mm carriers were exclusively S&W Model 59s.
At the next department, we were issued S&W Model 15s and carry ammo was WW 158 grain LSWCHP+P (Chicago load). After probation, you could carry any 6 shot revolver you wanted, after approval by Range Officer, as long as it would chamber the issue round and had a 4 inch barrel. Investigators could carry 2 inch J frames. The majority of the department stayed with K-frames, either the issue M15 or a 19/66, a couple of us, me included, carried Pythons, and one guy carried a Dan Wesson.
Both of these departments were in suburban Chicago (Lake County), and to the best of my recollection, no department carried magnum ammunition. I can't remember anyone I worked with, and there were plenty of us young "gun nuts" who worked together, feeling undergunned with the Chicago load. Many of us wanted to carry autoloaders, like the Illinois State Police (Model 39s), and would have been perfectly satisfied with the Model 59 (I carried one as an off-duty gun from my first department) and the ISP load (WW 115 grain +P+), but the Range Officer was an old school NRA revolver champion, and it wasn't until he retired and a new chief came in that the search for a new gun started, and resulted in adoption of the Sig 220 in .45ACP, after I had left.
I don't think it was political correctness or public relations that kept us from carrying magnum ammo. It was simply that the Chicago load worked; it was effective, it was easy to control, and it could be chambered in just about any type of handgun that could be used for police work. Why try to fix something that wasn't broke?