I have one on my 16" .223 shore upper. Works great. I have a second one I picked up on sale for $60 with a $30 rebate. Waiting for a build.
My 2 cents, ditch the riser and look for either a .83" or 1" UTG lightweight riser. Skeletonized, pretty sturdy and cost me $9 shipped. It weighs 1.1oz compared to 3oz for the riser that comes with the Bushnell.