With the loading gate open the cylinder latch is supposed to be lowered to release the cylinder. If it does not lower enough to free the cylinder, either the latch or gate spring are damaged. If you look at the latch (out of the gun) you will see a cylinder shaped piece that sticks out the side of it. When the loading gate is opened,the gate spring contacts this cylinderical piece and lowers the cylinder latch to free the cylinder. I think what is happening is, you have to pull the hammer back part way so the hammer plunger can lower the cylinder latch and free the cylinder. Your revolver still has damaged parts inside.
I would replace the loading gate spring, cylinder latch,cylinder latch spring and plunger first. Also your reverse indexing PAWL,and spring. I would run a tap into the hole that the reverse indexing pawl goes in untill the hex set screw can be seated flush with the hammer mortice. All other internal parts need to be checked for damage and proper operation.
Again, I suggest it be sent to Ruger.
When Properly fitted and assembled, these guns are tough,dependable and will last a lifetime.
Some people can wreck an anvil with a rubber hammer.
Good luck!
Note, the hammer will not go " all the way down when fired". At that instant it is resting on the transfer bar untill the trigger is allowed to reset.