My agency authorized .44 MAG for duty and off-duty, but the guns had to be bought by the individual. The issued revolvers were either Colt Pythons (4" blued .357) or S&W M66's (4"), and later 686's (4").
Ammunition was initially issued one time for the people carrying .357 MAG, but you had to buy your own duty ammunition in any other caliber.
I knew quite a number of guys who carried 4"-6" .44's on-duty (and a smattering of .45 ACP or Colt).
I eventually knew a handful of other guys who had worked for different local agencies who had previously approved the use of .41 & .44 MAG revolvers during the older revolvers days. One of them used to ride motors at his former agency, and he really favored his S&W .44 MAG duty revolver.
I never got around to buying a Buscadero rig to carry one of my own .44's as a duty weapon (costly, even back then, as they were custom-made), but I did carry one or another of them as off-duty weapons. I used .44 MAG factory ammo when I took one of my guns to the range, which I bought, as the only qualification ammo available was some locally reloaded .44 SPL loads. Nasty enough clouds of smoke, and smudged cylinders and frames, to make me think they used Unique for their reloads.
As time passed, and the heyday of revolvers for duty use were far back in the rear-view mirror, we finally started to frown upon authorizing big bore Magnum revolvers for off-duty (especially when the new .500 & .450 S&W MAG guns were appearing). I don't think they'll approve of anyone carrying anything for off-duty chambered in anything more powerful than a medium-bore .357 MAG or .357SIG nowadays.