I've shot my 416N (16") out to 632 meters on steel (skinny torso sized) with an Aimpoint Comp M4. First round missed, 2nd and 3rd were hits. Probably in the worst conditions I've ever shot in, it was raining sideways and retarded cold, fogging optics and whatnot... I did shoot supported with the help of my assault pack (E-tool, cleaning kit (for the gun, not myself) 3 spare mags and some clothing). Most of my platoon all got consistent hits at the ~500m target. Unknown Norwegian Mil ammo.
I have shot at person sized targets at 740 meters (uphill), and been combat effective. However prior to this we did "zero" so I knew my hold (estimated to 4 meters up and 1.5m to the left (spindrift)) and I was capable of getting consistent hits in a ~1x1m box at a normal firing pace (10 rounds/min). After doing it with a 8 man squad (2 M82A1s, 6 416s) all of the targets were punched a bunch of times, so I'd absolutely consider it combat effective (considering that I have very little idea about what it would do to a human at that range). This was with SS109.
As a "fun fact", when I start to go past 400m I prefer to shoot my 416 like I shoot the M82 (and MG3). Hand on the grip and off-hand on the stock, with the rail resting in a "channel" that I shape into my pack.
If Aimpoints are for close range only then I guess you need to get your eyes fixed or work on fundamentals some more...