Larry is correct that if the gun was made before WWII it probably has 2 9/16" chambers, but not all of them do. I have a 16 built in 1933 with factory 2 3/4" chambers and it is so marked. For a using 16 gauge LC Smith, I would not hesitate an instant in having the chambers and forcing cones let out to 2 3/4" for ease of buying shells.