Were you using something bigger than the 2.5" square as an aiming reference
No, it's actually a 1.6" black square and I can just barely resolve it at 100 yards. I made up some targets specifically for this using the "aim small, miss small theory". However I do use a small aperture on my shooting glasses to help me see the front sight clearly when I am going for accuracy (or precision, whichever term suits best).
Arrgghhh... make that the rear