I put the Acog on the Larue 5/8 riser, and I am now able to use both sights (Iron & Acog) with just a minor eye adjustment. Before with the Acog on the receiver, the iron sights were completely blocked by the Acog. The 5/8 riser places the Acog high enough, where the iron sights are lined up perfectly through the hole underneath the Acog.
