What seems to be the issue? Hard to advise you without knowing what problem you're having.
But I'm going to take a stab at this and think you're having trouble chambering a loaded round. If that's the case and having fired these cases 3 times and on the fourth reloading and it being a 257 WM my guess is that the case stretched and needs to be trimmed. But again, I'm grabbing at straws here because I don't know what your problem is!