I purchased a Steyer Aug A3 version some time ago and mounted a Leupold Mark 4 CQ/T. The issue is the charging handle hits the mount adjustment knob that came with the optic. With this optic there is no other type of mount that can be used as it is a proprietary optic and mount. With the A3 version I can at least use the bolt hold open button to lock the bolt back instead of the charging handle. Still frustrates me though.