Remington No. 4 Rolling Block Rifle

[TimOD9857]

Hello Again,
Thank you so very much to all of you who helped me to identify my Rolling Block Rifle. Now I have encountered a new situation. As I was told the small lever on the right hand side is a lever so that you can take down or take apart the barrel from the receiver. I have made several attempts to take it apart with no success. The lever moves in approximately a 180-degree arc. No matter where I place the lever, how hard I pull, twist, and turn I can not get the barrel to disengage from the receiver. Am I doing something incorrect or is there a very simple trick to completing this? Once again I am very grateful to all of the help I received the first time.
Respectfully,
Tim O'D