Bought a spare top cover for about $10, removed the ratchet cog. Drilled a hole, applied liberal "secret high temperature bonding agent" (JB Weld) to a spare Troy Vtac battle rail (after grinding off the front bolt nub to allow clearance for the charging handle spring cover plate), and bolted it in place. I measured and adjusted it about 30 times to make sure it was true before it set, and when I finally got it to the range, I only had to adjust the Sparc four clicks down and two left from its previous zero on another rifle. Ghetto? Maybe, but the money I saved buys a lot of ammo for practicing. I did a similar mount on a FAL and it's still holding up after nearly two thousand rounds, so I know the JB weld is up to the task. You can buy these ready made, or in kit form, but I'm a cheap bastard and just couldn't be bothered to do that. :)