Re: sunlightaffect
Sun up sights up - sun down sights down is valid, but you also must consider light from the right and left.
Lets say you are shooting toward the south in an all day match. The sun will be coming from your left causing shadowing on the target and front sight. Later, toward the end of the day, the sun is coming from the right, again casting showdows.
I don't know about scopes but generally with my M1A, I have to crank 1/2 to 1 min to adjust, Same when clouds move in.