This problem is common with the WSM's. I have a .270 WSM that you can not reload brass shot in another rifle for with standard dies. You can neck size new brass or factory ammo shot in it, but the only way to use brass shot in another rifle is to size it with a small base die. If you reload brass shot in another rifle, it will chamber, but it is very sticky. Heres the kicker, it will not eject. You have to take a rod and drive it out. I tried turning the necks, inside cutting the necks, trimming short, etc. etc. and nothing worked. Small base die makes the once fired brass work, then I just neck size.
I borrowed a couple sets of standard dies and they all did the same thing. Thompson just cut a tight chamber. I am sure it is within spec, but must be right on the bottom end of the spec.