Inspired by

http://en.wikipedia.org/wiki/M61_Vulcan

What it does in IRL

Shoots quite a large number of munitions in an 'arc' allowing it to 'slice' aircraft and lightly armored vehicles in half almost.
Empties out on a single controlled trigger pull just about.

Modifying for the video game.

We take the same concept; high fire volume and low endurance. This would up the amount of damage against vehicles but significantly make it rather exceptionally useless against infantry.

Goals:

Destroys LAVs if you nail it right.
Viable Air to Air weapon
Very feasible HAV threat may required combined effort or very steady aim.
Feasible anti Structure threat.
All small turrets
No large turrets
Horrendous anti equipment and anti infantry ability.
Low Field Endurance.
Viable Ground to Air for HAVs or LAVs to use
Harder to Fit than standard Turrets making it a purposeful choice of building the entire vehicle fit AROUND this gun rather than having it just because.
Same unlock convention as infantry variant weapons are +1 of baseline's required level.
Fast Reacting victims can throw up their hardeners to out survive the endurance of the gun or buy a moments respite.
Would make fitting ammo caches very appealing again to extend endurance.

Prefix Names possibles

'Burst' (historically weapon variants for vehicles do not follow the same naming convention as infantry)
'Compressed' The idea that you are compressing your damage window to do the high amounts of damage in a short amount of time. Was previously used may not be accepted.
'Accelerated' the idea that your weapons are overlocking to shove as many rounds out as possible. Was previously used may not be accepted.
'Impact' to emphasize its hard hitting this has not been used before so should be good to go.

Possible Skill Bonus 'Synergies'
ADS skills should start including Hybrid cooldown rates instead of ROF.
SLAVs reserve ammo bonus
MHAV Damage Bonus
EHAV Range Bonus

Blasters - Should feel like a Burst HMG when it goes off, heats up quickly allowing at most 3 bursts before seizing up, the entire magazine may have up to 6 bursts, and only 2-3 reloads. Could be shifted to have no reloads and massive magazine making burst management the only thing the pilot has to focus on. This will have the best on pressure and endurance of the three but lowest overall damage.

Rails - Not to be left out of the race the rail variant would rapidly fire up to 5-10 shots after hitting its max charge which takes a slightly longer than standard time to achieve to help prevent misfiring. The rail variant will always overheat but in terms of relationship it outstrips the other two in accuracy, range, speed, and alpha strike damage while suffering in the rof and dps department. Great for soft low HP vehicles or vehicles with low armor repair rates.

Missiles - A 'cluster' bomb like shotgun spread makes it a carpet bombing like pattern making it very deadly against large targets. Smaller targets can enjoy the lack of splash as these missiles are more kinetic kill vehicles instead of the standard explosive. The missiles will be the premier anti structure and anti large vehicle turret featuring mid ground on many attributes.

Just note that all of these turrets will run dry real quick in comparison to their non av variant cousins this would allow counter vehicles to arm up and get to the field to face the armed vehicle while AV infantry can now provide cover for their vehicles.