When you have it open and spin the cylinder, watch the ejector rod to see if there is any wobble. If none, I'd take it completely apart (remembering the ejector rod is left handed threads) and clean it really good and lube where it goes through the crane. It should spin VERY easily. And while you have it disassembled, you might as well give all the other parts a good cleaning also. I've had other Sixes come into the shop with the complaint that it wasn't easy to cock, DA was hard, etc. etc. I would take them completely apart, and they would first get a long bath (30 min) in the ultrasonic bath and then inspected, lubed, and reassembled and VOILA, smooth as a babies butt after a bath.