Tracker,
Based on your first post it sounded to me like you were just winging out shots. however, now that I see the scenario. box blind, wind, you shot out to 300 yards etc and know your BDC equipment. You were talking a chance, but everything for a 600 yard shot was in your favor. congrats. sorry I came off the wrong way. just seemed like one of those "head shot on deer posts".
anyway, congrats and sorry to turn this post to crap on you.