The idea of scrim is to break up the shape of a weapon. Shape is one of the reasons a person is seen, either their shape or the shape of the equipment they are carrying, ie rifle, helmet, webbing. Some of the scrim jobs I've seen out at my site look like they've wrapped the rifle to give as a Christmas present. It does assist with preventing shine, another example of why things are seen but there are much better ways of doing this than scrim. If you want to use scrim ensure that this breaks up the shape of the rifle, things like tape, paint ie cam jobs etc are much better ways of eliminating shine than scrim due to as someone said above obstruction of sights etc.