I think ur looking at the wrong drawing. Even the one you posted shows .277" neck Diameter +.002" tolerance.The neck diameter on fired brass is 0.268". The brass would have had some spring back from say 0.269". The maximum neck diameter on the chamber spec is 0.267"
The diameter of the brass body by the shoulder on fired brass was 0.267". The drawing of the chamber spec shows a maximum of 0.263".
I think ur using the wrong comparator. You should be using the .400" comparator. If that won't go over the neck there is big issues.It hangs up about .040 from the case body. It'll go in so far, but expansion at the body/ shoulder junction stops it. Therefore there is no way to measure shoulder bump short of resizing long and working back.