When I started in Law Enforcement. in 1972. Most officers in my area of Southern Illinois carried a large caliber Revolver. I personally in my Law Enforcement career have carried S&W M&P, S&W model 10, S&W model 28, Colt Trooper, S&W model 686, Glock 17, Model 1911 in both 45 caliber and 38 super. I think that the 357 magnum was popular because we mostly worked alone in a rural area which usually meant that if we needed to use our Revolver it was at a longer distance. with a possibility that we would have to shoot through automobile doors.