Winchester's Super-X .22 WMR 40 grain jacketed hollow point (JHP) and full metal jacket (FMJ) bullets--Winchester offers both--have a MV of 1910 fps with ME of 324 ft. lbs. from a rifle barrel. Fired from a 6.5" pistol barrel the same loads register 1480 fps MV and 195 ft. lbs. ME. Note that rifle ballistics of this load are nearly identical to the 40 grain 5.7x28mm factory load as fired from a sub-machinegun length barrel and from a pistol barrel the 5.7x28mm is only a puny 21 ft. lbs. of kinetic energy ahead of the .22 WMR. I have never heard that semi-automatic .22 WMR squirrel and jackrabbit rifles were considered a particular threat to police, nor have I ever heard the .22 WMR described as a "cop killer" handgun round. Actually, the .22 WMR is considered a "mouse gun" caliber by most handgun authorities.