After departure the nose gear unsafe light remained illuminated Peter gear retraction. Attempts to get a safe light on the nose gear in the extended position was unsuccessful and when the aircraft landed it settled onto a partially retracted nose gear. Inspection of the aircraft revealed that the nose gear strut had not fully extended and that when the gear was retracted the nose gear tires caught the nose gear doors preventing them from opening. The gear retracted against the gear doors causing failure of the retract jackscrew. A microswitch which cuts the gear motor off when this condition occurs was found out of adjustment and did not operate. Additionally it was found that the mechanics who did the last gear retract test on the aircraft used a maintenance manual for an earlier model aircraft which did not have this safety switch thus failing to check it for adjustment. No reason as to why the nose gear strut did not fully extend was found.