what work well on the range dont made it a good battlefield weapon. SA21 is too heavy, the laser thingy made the front of the rifle heavy, need a battery to work (which may not be available in war time). So in the end, u could end up with a heavy rifle with a simple 4x scope. I think the sharpshooter scope which work just as well plus M16A1 still lighter than the SAR21. A good battlefield weapon must be light, durable, simple to use, not many parts and should not have electronic gadgets mounted. i think the iron sight on the SAR21 is a joke, if both laser plus mounted scope become out of action, then SAR21 is as good as junk.
A M16A1 with an M203 attachment is about 500gm heavier, and i find M16A1 with M203 attachment is totally balance when firing live ammo. I collected $200 for my ORD shoot with a M203, the M16 barrel dun jump due to weight of the M203, so less time wasted in finding target 12 down range. While it a handicap when going 300m run down compare to other M16s firers but i wont trade it for other weapons.