What really helps the flex of the upper on this rifle, and accurcy to a point: is simply attaching a two or three inch or longer, low riser block between the upper reciever and the handguard, at least an inch or two on both sides of the connection point, stiffening the barrel connection point and also better securing the handguard. This acts as a very secure brace. A 5" low riser block is perfect, with irons, but probally will interfere with optics...Use what's best for your optics, but any number of combinations can be used. You can then remove the handguard end cap, or ream it out some and and free float the barrel, and the handguard will have much less flex on resting points, and or excessories. ...............best regards Plum