Your local agency recruiter/training person will tell you what they approve and/or carry.
First place I worked issued S&W 5906 9mm's. After 3 years the new Chief allowed personal Sig 226 or Beretta 92's if the officer wanted one. (I was there 3.5 years)
Second place I worked issued (still does) 4" M-66 .357 revolvers... No one has an issued gun, every one has their own auto. (Revolver calibers Ok'ed are .357, .44 Spl. .45 Colt) Auto calibers may be 9mm, .40, 10mm or .45. (I was there 13.5 years)
Currently I work where issued are Glock 19's, but one may carry what they want if it is Ok'ed. (Some 1911's, a Taurus .45, 3 or 4 Glock 34's, 1 Xd .45, even a PPK/s on an administrator that I recall). (Been here 7 years)
Good luck!