Excellent zero targets, Dave!
Stephen - I agree that a boresight is just intended to get "close." But, the new laser sights are so much more accurate than the old optical boresighters, you can get much closer. I like to boresight a rifle at 50 yds, then zero (live ammo) at 100. Haven't checked the ballistics of the .223/5.56 flight path, as my experience with tight zeros has always been with a .308 accurized bolt-action and match-grade ammo. That round crosses zero at 50 and 100 yards. For those of you following, that means if you are zeroed at 50 yds, it will be zeroed at 100, because the flight path of the bullet is still rising when it crosses 50 yards, and has fallen back to the same point at 100.