Howdy
Chiming in a little bit late, but here are a few comments.
First off, ANY double action revolver will ALWAYS have a lighter hammer fall when fired double action than when fired single action. That is the nature of the beast. When pulling the trigger double action, the mechanism releases the hammer slightly earlier, with the hammer spring compressed slightly less, than when firing single action. That is the way ALL double action revolvers work, at least all I have ever handled. In the old days, when cocked single action, Smith and Wesson hammers went back a lot further than they do today. The Short Throw hammers were developed because the engineers realized that when properly assembled and tuned, the amount the spring was compressed when fired double action should be enough to fire a primer. So there was no need for the hammer to go back a whole lot further for single action shooting. I don't recall exactly when the change was made to the Short Throw hammers, probably sometime in the late 1940s or early 1950s. Anyway, even though the hammer force is slightly less when fired double action, the revolver should still fire reliably in double action mode. Your hammer seems to be right at hairy edge of what is acceptable.
"the cadillac of 22lr revolvers, the best 22 lr revolver etc, etc.."
With all due respect, NOTHING S&W is making today is worthy of the term 'Cadillac'. Many years ago there were inspections after each machining and assembly step. S&W seems to have largely done away with most inspections today, in an effort to keep manufacturing costs down. Today, the customer is the final inspector, and as you have probably discovered it is less costly for S&W to repair bad guns that slipped out the door than to employ an army of inspectors.
Some photos:
I bought this Model 617-6 slightly used a few years ago. It shipped in 2003. I don't really care for this revolver, hate the heavy full length underlug. The only reason I bought it was I was shooting a steel match and had to get eight aimed shots onto a target in 15 seconds. Could not do that with a six shooter. I changed out the ugly rubber grips for some nice wooden ones a while ago, but I don't seem to have a photo of it with the new grips.
Correction: Here it is with the wood grips. Walnut I believe.
Study this photo. Notice where the firing pin has indented the rim. This revolver never misfires. That is where the firing pin should strike the rime.
ALSO, notice how much space the counterbore leaves around the rim. Contrary to what some think, this revolver can be dry fired until the cows come home and the firing pin is not going to strike any part of the cylinder. Dry fire it all you want, however stop using spent 22 rimfire cases. After a couple of strikes, the brass gets dented enough that it no longer cushions the firing pin. Rotating spent brass to expose a new portion of the rim to the firing pin is OK though.
Here is the front of the yoke on your 617.
Here is the business end of the yoke of my 617-6. Notice how much less slop there is around the hinge with mine.
This 32-20 Hand Ejector left the factory in 1916. The gap around the yoke is almost invisible. That is the way it should be, but S&W will never produce a revolver this fine again.
Anyway, I hope S&W can fix the problem with your 617. You should not be getting all those misfires in double action.