S.B., I am just eying the forcing cone, no measurement involved.
David Carey, there is no magic number of rounds for barrel replacement, when the 460 first came out, people that had nothing better than put numbers out were saying 1500 to 2000 rounds the barrel would have to be replaced. Well, I have about 2000 rounds through mine with no ill effect at all. I suggest you call S&W and talk to the tech department and they would be able to give you all the information you need.