Many thanks. I had assembled the two rifles without either spring. I've now put back the lighter spring. Not that it makes a greatly noticeable differene. But I suppose it is one less item to lose if kept "on" the rifle.

I think that you are right about the washer. I certainly haven't seen one in that position in any other weapon. Nor does anyone else I ask that has knowledge about the ZKK recall it. As you say one owner's possible "fix"?

I prefer the aesthetics of the normal trigger and don't like either "set" or single-pull triggers. I'll have to live with the single-pull anyhow. That, and the safety, are my only criticisms of the design of the arm.

What I do like is the "peep" aperture rear sight. Both my rifles have it.