I purchased a .30-06 field gage. I have only 2 M1903's that are high serial numbered. The rest are the lowly, low numbered, but among my favorites. I shot one of them long before I knew anything about heat treatment problems. One rifle (Springfield 652,952, 5-17 barrel date) has an I 8 bolt. It closed easily on the field gage. This bolt would not close on the gage in a couple other rifles and closed easily in another rifle. Using other bolts ( I II and J 5) in 652,952 resulted in non-closure on the field gage. Wow. I had no idea how much difference there is in bolts and how it affects headspace. What happened to interchangeability of parts? Anybody have comments? Help for the dunderhead?