Kavorka:  Is it possible you have reversed the bowed flat spring?  It should only bear on the door (hinge pin cavity) at the spring's center curve.  Also, there is a notch in one end of the spring that is to clear action parts.  The radiused end of the spring goes to the rear and the notched end goes foreward.
  If every thing is clean and lubricated (pipe cleaners work good on door 'hinge pin cavity'), you should be able to hold the magazine door in position against spring pressure and wiggle the hinge pin back into place.  It helps to repeatedly squeeze the door against the spring pressure to align the holes as you wiggle the hinge pin through.
  When fully inserted, rotate the hinge pin so that the  attached flat spring snaps into place even with the receiver bottom.  (Make sure your hinge pin is straight.  Try inserting it through the door while off the rifle.  Try inserting it in the action minus the door and spring.  If it is bent, it can be straitened with a plastic mallet and hardwood block).