Congealed crud can be loosened up or removed by the liberal application of lighter fluid, Coleman lantern fuel, gasoline, acetone, or boiling water. If you have a bolt action, dismount the scope, remove the barreled action from the stock, go outside, far from any flames, pour your solvent into a container, and let the offending machinery soak in it. Now try the action. If it's been freed up, let it dry out and put the gun back together. If it's still clogged, repeat the treatment. If you have a rifle other than a bolt action, removee the scope and the buttstock and proceed in the same manner.