I recommend you do not force the cylinder open, I believe that's what was tried with this gun.
If you are unsure as to what to do it might be best to take the gun to a smith in your area that's familar with S&W revolvers and let him take a look at it.
I did discuss the matter with a Gunsmith, and here's what he told me: And showed me, even though my gun wasn't experiencing that problem at the time-- he had it for another reason.
If you're on the range and can't open the cylinder because the ejector rod has unscrewed you MAKE SURE all rounds have been fire from all cylinders. Then push in on the rod, or hold it if it's unshrouded, and don't let it turn. Now pull the trigger a few times until the left hand threaded rod screws itself back in as the cylinder rotates to the left.
Open cylinder.
He then removed the cylinder screw (if it was loose to begin with, this could have been the problem), removed the cylinder, crane, etc. He placed the knurled end of the rod in a vice (no, it wasn't dinged or marred), placed two empty cases, opposite one another in the cylinders, and simply turned the cylinder to the left to screw it in. I didn't ask him about Lock Tite.
In another thread, Mike Irwin described a method that included using a wedge between the cylinder stop and the cyl. and another between the ejector rod and the cylinder bolt, which would allow the cylinder to be opened.
Anyway, about this gunsmith. After stripping my gun down in about 1 minute---as in all internal parts-- he looked around for the problem, which was a jammed cylinder stop that wouldn't move. He found a tiny piece of metal wedged in there. He examined all parts, including the firing pin nose (of course) and couldn't find where if came from. He said that the only other place it could come from was the back of the firing pin inside the hammer where we can't see it.
That was the problem, and he replaced the firing pin. It had broken because the teeny little spring had been missing that positions the fp properly so it doesn't batter the firing pin busing and eventually damage the fp.
He then took his stone to the hammer, and rebound housing (no more than 30 sec.s), lubed and reassembled the gun in about 5 minutes (testing stuff as he goes along), after replacing the rebound spring.
The gun, a 586, had been reasonably smooth to begin with, but now it felt like a world class trigger job. He then checked the hammer tension which met the 3.5lb. S&W standard and I was all set. It was at this point that he showed me the trick re: the unscrewed ejector rod after I asked him about the problem.
I like making trips to his shop, what I learn is incredible, and when he talks, I listen. That's why I wanted to point out that method of dealing with the ejector rod, though he didn't claim it was any big secret.