Late to the show, didn't read more than the first couple of posts. If the bullet is still in the forcing cone, but back enough to block the cylinder, try this. I had the same thing happen not too long ago with my M-19-3. Prevailing wisdom seems to be trying to drive it back into the cylinder, but IMO you run the risk of putting undue strain on the cylinder and center rod, possibly inducing end play. What I did, and it worked perfectly, was to hold the gun muzzle down by the grip, and smack the muzzle with a plastic mallet like mechanics use. The plastic won't damage the barrel; the inertial force will drive the bullet further into the barrel, enough so you can unlock and open the cylinder. Then you take a wooden dowel and drive the bullet backwards through the forcing cone. You hold the gun firmly enough you don't drop it, but loosely enough it can move backwards rapidly when you smack the muzzle. It might take two-three sharp blows to move the bullet enough, but it will move.