Well this is how I do the wby's. I would stick with the 300 wby you have, it's a great elk rifle and the 30's have a great bullet selection. I use lilja of kriger barrils. I think both of the barrel makers will only flute a #5, which really drops the wt. down to about a #4 anyway. Put an 11 degree crown on the barrel. Find a smith who can cut the chamber and throat seperate, and have him cut the throat to the loaded round that will fit you magazine. Maybe .030 to .050 shorter than your loaded round. Now your gun is chambered perfect for the mag. As for the muzzel break, I'm not a really a fan of them, but if you must have the smith put on on. I've done a pile of these wby this way and it's worked great.