Paul, Yes and Yes. It is most effective to use a scope that has accurate and repeatable elevation and windage adjustments (just like good iron sights). As I understand it, the rifle may have BUIS's but I assume that they can't be used during competition since my understanding of the rules is that if iron sights are used in lieu of an optical sight, they must be the carry handle variety. The actual wording is "Alternatively, the rifle may be equipped with issue-type metallic front and rear sights with a maximum sight radius of 20.5inches. Metallic sights, if used, must have an M16 type sight design with the rear sight in the carry handle and the front sight in the standard M16 location." Rick