Rise works for an inexpensive drop-in as does Davidson Defense from Delta Team Tactical. https://www.deltateamtactical.com/ar...er-system.html Been running half a dozen of them for a few years now and they are holding up well. The Fostech Echo IIs are my favorite when running drills. https://fostech.com/product/echo-ar-ii-trigger/ For all out precision I'm still a fan of Timney though.