Put together my lower over the weekend and installed the MR 556 upper kit. I have the HKey 9 inch handguard on mine and was attaching rails, foregrips, bipods etc and I've decided this HKey rail has to go. I's prefer a quad rail or something like the Geissele rail. I could do keymod as my other ARs have keymod. I've had stuff come loose from both keymod and mlok under heavy use hog hunting at night getting in & out of trucks and changing what is set up on the rifle - quad rails or rails that screw on seem to be the best bet for me. Recommendations appreciated. I'm leaning toward the Geissele rail right now although the price on the HKParts DMR quad rail is very attractive but haven't had any experience with their stuff.