Someone said projectile-based weapons widen the skill gap, well that depends on whether the projectile weapon is hitscan or not and whether it's got a consistency to its trajectory.
The Halo 3 BR has a spread, it's completely random every shot you take. The first bullet is basically a straight line shot, the second is off the path a bit and the third is the most innaccurate, all intentionally designed this way. Since each bullet counts as its own packet in Halo 3, it's very difficult to say that someone has skill with a BR when there is zero consistency with the weapon.
In a game like Halo 2, the BR isn't difficult to shoot because there's massive auto-aim (the bullets bend toward the player model) and the sticky aim is massive, so you really just have to point and shoot, the game takes care of the rest, but in my opinion, I'll take that consistency over Halo 3 any day.
If a gun is going to be non-hitscan, then the bullets/projectiles need to be consistent and shoot in a straight line. This way the player aiming at a moving target is forced to adjust their aim, lead, etc.
No amount of good aim is going to make someone be consistent with Halo 3's BR. It's still a slot machine weapon.