Hi I was wondering if someone could help me out, i am getting a cooper model 21 phoenix in .204 ruger threaded for a sileincer. Does any one have one of these and know what the end of muzzle outside Diameter of there barrel is? I dont have the rifle yet as its at the dealer waiting to go to the gunsmith, the reason I need this size is to work out the best thread size I can use on it, to keep as much of my barrel Diameter as possible.