Do the 66 and the 686 use the same hand spring, the coil spring inside the trigger that puts tension on the hand? I lost mine.

I decided to open it up. Probably the wrong decision, but I thought I'd give it a stoning before sending it back again. That smoothed 99% of the trigger pull up, but made the hitch stick out like a sore thumb. Now it's like there's a 1911 trigger break in the middle of the trigger pull. If I could just get that out of there, This trigger would be like butter. I'm going to keep looking at it. I learned that it's not the interaction between the trigger and the cylinder stop. With the rest of the guts out of it, the trigger moves the cylinder stop without a hitch, especially after some gentle stoning. It must have simply been a coincidence that the hitch happens at the same time that the trigger releases the cylinder stop. I'm stumped.

I just ordered a new hand spring, but I'd like to test out what I've done so far, so can I pull the hand spring out of a 66 and try it in my 686?

I'd loose a ton of money if I did that. As soon as I finally found this gun in stock I paid full retail for it. $759 + tax. I'm not a good enough salesperson to tell a buyer that I bought this gun, don't want it now because it's defective and the manufacturer can't fix it, and still recoup my money on it.