You have taken section fire to mean sustained fire. and drawn the conclsuion that hte weapon will lose accuracy.
In a sustained fire role the beaten area will increase, 2nf of foot has given you the schematics for waht this area is, the large beaten area will suppress an enemy and despite lackng accuracy encourage an enemy to stay down. An Light machine gun or assault rifle is not a sniper rifle and has a role to suppress as much to neutralise.
(on re-reading your post (I hope) you have assumed 8 rounds fired simoultaneously means a “burst” of fire - it does not - that would be 8 rounds fired “sequentially”)
I did not however make reference to sustained fire I referred to section fire. This is where eight men each take aim and fire a shot or shots, Depending clearly on the “type of fire” requested by the Section commander or 2ic. Section fire is more effective than individual fire. The accuracy of the individual weapon does not increase merely by being fired on concert, but the fact that 8 bullets each travel toward one target implies a higher chance of a hit.
Consider zeroing your rifle. you fire 8 shots at the centre of a target, none hit the bull, but with any luck the median of the strikes will be the centre of the target. The individual discrepancies of the individual weapons are minimised by the fact that 8 weapons fire rather than one.
I am running out of ways to explain this, if I have to throw one stone at a target fifty feet away I might miss. if I pick up a handful of stoness at a target fifty feet away, Ill probably hit it with at least one. Section fire - not sustained fire.
Bullet drop etc - yes we all know this, I can suck eggs thanks, but nevertheless a useful story to demonstrate you have knowledge of firearms. however, Bullets do not rise when fired from the barrel, the bullet will continue straight and level until gravity and the planet earth result in the bullet hitting the ground.
The Bullet cannot rise! no article of physics allows for this. For a bullet to travel upwards their would have to be a force pushing it skyward. The only force acting on the bullet is directly from the rear (if we remove recoil for the sake of clarity) the only way in which a bullet will rise from the horizontal plane is through canting the scope, but still the bullet flies level (do not read level as horizontal) until it loses momentum and gravity brings it back earthward.
Bullets to not travel in curves from muzzle to target! After leaving the muzzle, the trajectory is straight - in continuation of the barrel, followed by a point where they lose momentum and gravity pulls them earthward again.
Consider artillery, barrels of which are pointing well above horizontal in order to give them range your range increases by giving the projectile more time in the air by aiming it away from the floor, if bullets “rose” and you did say they “rise” I have been lied to by all my physics books!
Finally
The question was whether one could “see” a target at 600, the skill with shooting is not to see the target its to control your breathing, pulse rate, fine motor skills, large motor skills, shakes and nerves and hold the firing point long enough to pull the trigger before you lose control of one of those listed aspects. Yes I have competed in target shooting, but thats beside the point.