I seem to remember someone doing testing of a regular revolver (not a Nagant) with a can and measuring the sound of the cylinder gap. I thought it may have been Destin from Smarter Every Day but I don't think it was him now.
I don’t know about the testing you mention, but I have read about mods done to revolvers to allow them to be suppressed. It involved a clamshell type cover that went over the cylinder.