Pentagon Light add, currenty published in Jan 06 SWAT, pg 37, probably also in other rags.
It's an M-4 with regular M-4 handguards. The mount is a picatinny rail that spans the entire length of the HG, but the rail is oriented vertically. I'm assuming it mounts in some bottom vent holes and then makes a 90 turn to the vertical. The Pentagon light incorporates an Arms 17S throw lever mount, but I'm assuming that's just the mount, that the rail is a separate deal. Anyone know who makes such a rail?