Coyote Sniper,
It is because the WSM;s are fatter than the 7mm and 300 Win Mag that makes it hard on the encore. There just isn't enough meat left around the chamber after they cut it. Also the encore does not lock up like a bolt does and relies more on case expansion causing the case to grip the chamber to help ease the pain on the frame.
I THINK. Please let me know, anyone, if I am incorrect.