Ruger sells a ton of their AR-556 rifles and with dealer prices often under $600, it’s easy to understand why. Ruger, being Ruger, did the typical Ruger thing and included some proprietary parts on the AR-556 that make it just a bit more difficult to customize (versus an AR-15 with standard parts). One of those parts is the FSB which is very nice but also very non-standard. This is where Custom Defensive Products and the BLAM-R can help.
The BLAM-R is an accessory mount made specifically for the Ruger AR-556 FSB. It is designed to mate with the specific contours of the bayonet lug and provides a sling mounting slot and QD sling socket on both sides along with a 4 slot Picatinny rail on the bottom.
This might be the easiest, all-in-one, way to add a forward sling mount and light mounting solution to the AR-556.