here is a video about the Mannlicher Schönauer bolt that is similar but not the same
http://www.youtube.com/watch?v=IErJa8XRbwY

I uncock and press the bolt head against the table than push the safety and twist the bolt nut of.
hold the bolt head carful against the table because the firing pin comes loose and press against it when the bolt nut is off. you dont have this later 90 degrees milling groove like the Schönauer but a conventional thread.