Since our (KAC) FF RAS allows the host weapon barrel to "free-float", there is accuracy enhancing potential there, especially with match grade ammo.
Our M4 Carbine RAS and M5 Rifle RAS "touch" the host weapon barrel in the same way as issue plastic handguards. So these are not classified as FF.
There is only one screw at the rear of the M4 or M5 RAS; at the rear, where it forms the top of a "triangle", and when its tightened, aligns the RAS to the barrel nut. The two lower points of the triangle are two oposing dowel pins that index to the barrel nut's 10 and 2 o'clock gas tube slots. This is a patented and very secure (i.e., accuracy) assembly.
At the front of each RAS, there is a spring loaded spacer that minimizes the "warp" or walking effect of a hot barrel "moving the rail" out of its normal "cold" alignment to the sights. However, this is a very small deflection and hardly measureable with GI ammo.
ColdBlue sends...