1860 Army can the cylinder be removed for reloading on the bench?
Like the others said, tap out the barrel wedge from the side of the barrel. The wedge won't come all the way out because the little screw head will keep it from falling out. (That's what it's there for.)
Pull the hammer back to half cock and rotate the cylinder slightly so the lower two chambers are straddling the loading levers ram.
Release the loading lever and pull it down like you were loading the gun. This will force the loading ram against the face of the cylinder and result in the barrel moving forward. Be sure to check that the barrel wedge hasn't gotten caught in the slot in the cylinder arbor.
Grab the barrel and pull it forward to remove it. Once it is removed, the cylinder will slide forward easily off of the arbor.
Leave the gun at half cock while you are doing all of this.
To replace the cylinder, with the hammer at half cock, slide the cylinder onto the arbor. Push the barrel onto the arbor, making sure the two holes in the lower area of the barrel engage the two pins in the frame. Once they do, push the barrel onto the arbor until the lower part of it is resting on the frame of the pistol.
Once this has happened, push the barrel wedge back thru the arbor hole and LIGHTLY, tap it in place.
The end of the wedge does not have to stick out of the other side of the barrel. It may do that but as long as the end of the wedge is flush with the side of the barrel or sticking out just a little bit, all is good. The little spring on the wedge is not supposed to hook onto the outside of the barrel. Some people think it should but if they do drive the wedge in far enough for that to happen there is a good chance they will damage the wedge or the slot thru the arbor. They will also have a terrible time trying to get the wedge back out the next time they want to remove it.