Flyboy got the idea right about the bullpup layout of the FAMAS...though he worded it a little awkwardly. Kind of a cart before the horse situation.
The primary purpose of a bullpup layout is to shorten the weapon, making it easier to use in tight spaces, such as close quarters battle; so a bullpup weapon like the FAMAS is no more or less accurate than a standard assault rifle layout, but gets the advantage of a shorter overall length.
The chamber of the weapon, where the bullet starts its travel after the trigger is pulled is located behind the grip, above the magazine, rather than in front of it, so you save a few inches, allowing the barrel to appear shorter, without reducing the length of the bore that the bullet travels; as we know the longer the bullet stays in the bore, being pushed by propellant gasses the more velocity it builds up.
As soon as it exits the muzzle, 'muzzle-velocity', it is the fastest that bullet is going to travel...and it immediately starts slowing down.
Bullet speed has more to do with effective range than accuracy. On a level trajectory, a bullet will begin falling under the influence of gravity as soon as it leaves the muzzle; so the faster it goes, the more distance it can travel before it hits the ground.
As soon as you raise the muzzle, (as well as due to effects of atmosphere) a bullet will arc on a parabolic trajectory.
A speedier bullet can give you a flatter trajectory, and will be theoretically easier to aim, but as long as you have a good calibrated sight, you can be accurate with a slower bullet, even if you have to 'lob' it in on a more curved trajectory...
Blah, blah, blah. I'll shut up now.