Think I just found and answer to my own question... I removed the bolt handle and found there's a good bit of slop / play in the connection between bolt body and bolt handle, so the position of the bolt handle varies depending on where the bolt handle is at when you tighten the rear allen key bolt. Moved the handle and tightene the allen key bolt so that the handle touches the tang a little earlier when closing the bolt, and that made the lugs come to a rest at about 90 degrees.