Saintpcr:

From your description, I am assuming the hammer is resting on a fired cartridge - correct? If so, this makes things a bit easier. If not, I'd suggest taking it to a gunsmith. Assuming the hammer is resting on a fired cartridge, I'd suggest starting by removing the leaf spring screw on the frontstrap of the revolver. This should take the tension off of the hammer and allow you to gently cock the hammer and free up the action. If this doesn't work, then try to see if the ejector rod is loose. Use your fingertip, or a piece of leather and try and turn the ejector rod. It shouldn't turn. If it does, simply screw it in tighter (by hand), and you should be able to open the cylinder.

Best of luck,

Dave