The issue with using the go gauge to compare modified cases with is that not all rifles use the Savage head space system where you can simply screw the barrel down on a go gauge , then lock it down and be done with a perfectly head spaced chamber.. Rifles like M70's, Rem 700's and my 1903A3 are usually short chambered when the barrel is screwed in then finish reamed . Sometimes they are reamed to slightly more than optimal depending how good the smith was doing the finish chamber reaming. Especially the older surplus military rifles that may have passed inspection with a field gauge. This is why I want to take a fire formed case formed in MY chamber, then size it setting the shoulder back between .001 and .002" then drill and thread that case which is exactly to the same dimensions as the cases I will be loading.. The Hornady threaded cases are to spec, but not necessarily to MY chamber. I hope I make sense with this. Maybe I'm not.