In looking at your photo, it would appear that the sight is not in what is called mechanical zero,(centered) but rather the right side of the windage drum screw shows some 7 threads and left side shows only three. Irregardless, even with that much windage on the rear sight, don't believe it should impact on the receiver when folded, but may well be the nature of the beast?? Is the front sight on the SR556 capable of windage adjustment? If so, center the rear sight and adjust left or right w/ the front sight and maintain centered position for rear. Can't imagine needing much windage adjustment for this type of firearm, but perhaps others can share some insight.
martin