Jimbo. The gas ring goes over the arbor between the cylinder and the barrel lug. Colt used one in the 1872 open top cartridge revolver to maintain headspace for the cartridges and to cover the arbor at the barrel cylinder gap. Some use them with percussion revolvers to cover the arbor and to keep the cylinder back against the recoil shield that keeps the hand from being short timed as it pushes the cylinder forward during rotation on guns with excessive barrel/cylinder gaps.
I guess mine were what you call a floating ring, just a spacer between cylinder and barrel. I had thought it would make the action smoother by eliminating the drag of cylinder against the barrel face and prevent fouling from binding the cylinder on the arbor. It really didn't make a noticeable difference.