The 'flush magazine' probably refers to the not-unusual practice of making the magazine's door fit flush against the line of the stock's wood along the right side of the action. This conversion is detailed in The American Rifleman, I believe the article I saw was published sometime in the '50s or early '60s. Apparently the conversion made the rifle a LOT easier to carry in the field and some folks even thought it looked better....
Regards, Joe

You can lead a man to logic but you can't make him think. NRA Life since 1976. God bless America!