Using a sling on an AR-15 applies torque to the barrel or the float tube. This torque is the reason most shooters use a float tube. The torque causes some movement of the float tube and can cause cuff style front weights to shift slightly in the hand guard. Shifting weights can put pressure on the gas tube, which can cause misalignment of the tube with the carrier key. The end result is accuracy deterioration. The Martin front weight installs in the bottom of the hand guard and eliminates the possibility of a torque shift causing pressure on the gas tube. Approximate total weight of the Martin front weight is 3 lbs, 6 ozs. To order the correct Martin front weight, measure the outside diameter of your float tube at the front end of the tube.
Sinclair, Issue:5B, Page:251