Parallax Tactical is getting set to release a 17.5″ version of their FFSSR Handguard! It should be right at home on AR builds with barrel lengths of 18″ or longer.
I currently have a 15″ version of the FFSSR on an upper that I am testing. It is very rigid, has rails where I need them, and has the ability to accept just about any direct connect accessory that is meant for use with Magpul MOE Hand Guards on the slick portion of the hand guard.
The new 17.5″ FFSSR Handguard exists only in renders for now but it will be available very soon. Check out Parallax Tactical.