Lets be honest all four rifles are too effective for their own good. However it MAY be possible to balance them without changing the damage.

1) Add some actual dispersion - currently you can hit a target with pinpoint accuraccy, there is no need for leading your target or anything.

Now while adding projectile speeds for bullets would be overly intensive, we could at least have some dispersion even while ADS.

2) Add REAL recoil - the recoil on these weapons are pitiful at the moment not to mention that you go 15 rounds (520 damage) with absolutely none. Add recoil per shot, you can do it the hacky way and just move the barrel up a set amount after each shot, or you can do it properly, move it up, move it right, then move it down again (but not as much as it moved up) to increase immersion and feel of the weapon.

3) Remove the recoil reset function - currently even if you don't kill your opponent in the first 15 shots, you can keep firing until you stop hittimg him, then just feather the trigger and you are back where you started, completely nullifying recoil all together. You may have said its a feature but its not a very good one, it eliminates the need to readjust your gun after prolonged fire, which in turn reduces immersion, lowers skill level etc.

4) Add momentum dispersion - as you move you should become less accurate with your weapon, no matter how well you are trained. Simply add say 20% extra dispersion while moving, you could even add more during jumping if you want to discourage bunny hoping(wouldn't advise that but you could).

Only while not ADS, recoil as pointed out is pointless, you can still get 2-3 bursts before feathering the trigger, but with a burst rifle you feather it all the time, making it more pointless.

The Rifles would be balanced IF it wasn't so easy to hit the target, the potential DPS is high and rightly so, but it should require skill to achieve that kind of damage.