The iron sight can be toggled off, not the scope crosshair, as far as I know.
oddly im more accurate with the non-'true' iron sights <_< i like true, but untrue is just so much more accurate for me.
back fully on topic, what console are you on? you can also time it right where you aim, fire, and as soon as you fire in iron-sights/crosshairs, zoom out, and while you character is cocking the gun, he will still be aiming until he finished the motion.