Discussion with one of my Sons who is the Firearms/Training Officer for a large Agency concerning effectiveness of Police service weapons of His Agency. This Agency went from .38 Revolvers, to 9mm Glocks, to .40 Glocks, to .45 Glocks. Issue ammo has been Speer Hydro-Shoc. The most effective caliber for OIS was the .40 S&W. I was surprised that it was not the .45acp. His opinion is that .45 Glock large grip and weight could not fit the smaller Officer's hands. The .40 fit improved quicker recovery time for followup shots and accuracy. His Agency has now gone to the 9mm Glock Model 45 ?