This came up not too long ago and it wasn't the sizer that is the problem but the seater. Take your fully sized case and try them in the chamber before you load them gentally closing the bolt. Even if they are not bumped back enough they should drop right out of the chamber if you don't jam them, if they are too long the bolt shouldn't close or just partially.
If the fully sized cases fit well and loaded ammo sticks more than likely it is the sizing die and you are hitting the crimp ring slightly and shoving the neck back expanding the shoulder, it doesn't take much, easy cure back off the seating die a whole turn and re-adjust your seating stem. If the bullet is seated too long the bullet usually gets pushed back into the case and you will see the rifling engraved on the bullet and the OAL will be shorter than when you loaded it, or the bullet will stick in the rifling and you will pull the bullet out of the neck extracting
If the fully sized cases fit well and loaded ammo sticks more than likely it is the sizing die and you are hitting the crimp ring slightly and shoving the neck back expanding the shoulder, it doesn't take much, easy cure back off the seating die a whole turn and re-adjust your seating stem. If the bullet is seated too long the bullet usually gets pushed back into the case and you will see the rifling engraved on the bullet and the OAL will be shorter than when you loaded it, or the bullet will stick in the rifling and you will pull the bullet out of the neck extracting