I've got the blow back version, not sure if same set up on front, on side of cocking handle, by the front sight is a lever, move this clock wise, this should release the upper part of hand gaurd, when this is removed you will see by gas block in side of bottom part of handguard a small lever push this up you may have to use a flat head screw driver then the bottom part is now free
First pics are of lever and which way to move it, second pic is of the other lever inside lower part of lever finger pointing at it
You will need to use a little force, try a little side to side, up and down motion on the upper part while pulling towards stock, it will come off had same thing with mine and as you see I've changed the hand gaurd