Now, how do we get around this? Well, you start with headspace guages. If (IF) the rifle just barely closes on the "GO" guage with no play, (ejector removed) then you may, if the lug isn't too far out lap the bearing lug until the other one touches (DO NOT LAP THE LOOSE LUG) and then run a "no-go" guage through the rifle. If (IF) the bolt will not close (DO NOT FORCE) then that rifle would considered to be within specification and you've done nothing wrong. The loose lug is only out probably maybe .003 (?) and the headspace allowable is usually .006 between the go and no-go guages.
While I decry such workmanship I do understand that in continuous use the loose lug will probably be brought to bear through use - but I decry this emphatically!
Mr. Kuhnhausens book is a very well written and accurate book on any subject and I would obtain one!
The common practice on Mauser if you are using the stock barrel is to correct headspace by setting it back a partial thread and correcting headspace - and - if a factory rifle is out badly the proper cure is to remove the barrel, detail the action and correct headspace by refitting the barrel which, of course, ruins the open sight alignment! The Remington action is homogeneously heat treated and lapping will not harm it, it's an alloy steel.
I'm sorry you have experienced this but thank goodness you are smart enought to make this check. Congrats!