it is my understanding(or rather i read some rumor somewhere) that the irondot was temporarily disontinued as burris disontinued the fastfire optic and are now marketing the fastfire II which has a different bottomplate which was not compatible with the iron dot mount. supposidly the mount is being completely redesigned and reengineered to work with the fastfire II. i do not know why the dr. optics were phased out for the burris fastfire though...

i'm sure someone associated with larue will be along shortly to either further expand or to completly dismiss this rumor which i am merely passing along to you...