First if the gun was functioning before, Remove the forend and grip and soak it in solvent over night. Then see if it will work.
Two items on the Contender Gen1, if the oil in the gun has not turned to glue, the locking lug adjustment is done from the bottom not from the top, with 600 to 800 wet/dry with oil on a flat surface like marble or preferably glass. Next, the activation pin, looks like a dun-bell that works the barrel locking lugs with the tigger guard sloped arms, could be bent. If bent toward the muzzle, the sloped arms of the trigger guard that move the pin and thus the locking lugs forward will not unlock the barrel.
Either the pin is bent or the lugs are stuck by being jammed under the frame locking surface.
Take the forearm off, drive the barrel swivel pin out with a dowel or brass flat punch, remove the barrel by lifting up and pulling forward. Take the block retainer pin out of the block, that holds the locking in, push the lugs down slightly so they do no not go flying, remove the lugs, actuator pin and the coil spring. Clean and examine. Then straighten the actuator pin if necessary and take about 1/2 of one thousandths off the bottom of the locking lugs, on a flat.then Clean and oil, reassemble as normal and try the close, lock and cock hammer to check function the internal safety, then open. Repeat until you get 100% proper function including the internal safety.
Been repairing contenders for about 40 years.
