I"ve shot them so much in competition I think I almost married one of mine.

Anyway on a brand new one the parts could be so tight and not mated/polished that it could be a bit tough. I never would take my op rod out, to take the gun apart is not needed to clean and wears out the bedding area. Which kills accuracy. If I were you I'd just leave it as maching a piece away may make it more prone to come apart too easy later on after a few thousand rounds.

FWIW your dad was dealing with rack grade M14s that were probably pretty loose to start with and thats why those issue weapons come apart so easy.

Jeff