.357 +P+?
I may well be out of date with this expression....it used to be that the "+P" and "+P+" designations indicated a high-power load, oftentimes expressed on the retail box as "Police Ammunition". and the "+P" designation stamped on the cartridge rim It may well be that this expression isn't in current use anymore, although I'm seeing it shown as a result of a web search for "+P Ammo".