Regarding any lockwork difference the FBI 1076's may have had: If there was a difference, and that difference was part of the reason some of the FBI 1076's didn't work so well, which prompted their return to S&W, and S&W decided to resell the guns to the public, wouldn't they have probably replaced any different parts with standard 1076 parts?

If so, then all 1076's in public hands now would have the standard lockwork parts.