Good Mike- I don't own a M21 (yet) but have a 1938 Winchester Sales Manual page 40 says (re: M21) There is a screw in the breech end of the barrels, the head of which determines the depth to which the locking bolt engages the barrels. If the gun should appear to be loose it is merely a matter of turning this screw inward, allowing the nose of the locking bolt slightly greater engagement. This screw should be turned in until the top lever shows a tendency to stick when the gun is closed sharply, and the top lever allowed to snap into its closed position. When the top lever sticks under this condition, the screw is in too far and should be backed out just enough to prevent this sticking" There is also a cut away view drawing on this page showing this- So would Mr. Schwing's book on the great M21 also show this-why, incidently, answers (albiet from a Winchester-ian point of view- an earlier ? posed on this BBS- about closing double guns?? Huumm-RWTF
