The older ones with the "C" extractor have a barrel with the breech end recessed like a Rem 700. Newer barrels are flat-ended and newer extractors slide in a slotted RH bolt lug. I don't know if the raised ring for the rear sight dovetail disappeared at the same time as the bolt face style/barrel end was changed. Within one system, newer or older, barrels are interchangeable. 222 and 223 use the same bolt face.
What I haven't found out is if newer bolt heads will fit the older bolts so modern barrels can be used. Maybe a whole bolt could be switched instead. Midway has/had Savage bolts and bolt heads.
Bruce
Last edited by bcp; 11/18/07.