Well i just had a shot at getting an AC-130, i never use them tbh, i got it within 3 minutes and this is how.

Ground War TDM Highrise;

Class 1-

-Barrett FMJ
-Claymore (Wasn't used)
-OMA Pro
-Stopping Power Pro
-Steady Aim Pro

Spawn Snipe, got me 3 Kills. (This step, however, can be skipped and you can start at step 2 if you think you can get the kills.)
Changed to Class 2.

Class 2:

-Famas w/ Grenade Launcher
-Claymore (Wasn't used)
-OMA Pro
-Danger Close Pro
-Ninja Pro

Sat back behind my team mates and practically used them as human meat shields, they ran in, cought attention i sat back i stole their kills with a few tube launchers. This got me my predator missile.

I then switched to class 3.

Class 3-

-ACR (Optional) w/ Heartbeat Sensor
-Claymore (Was used for precausions)
-OMA Pro
-Hardline Pro
-Ninja Pro

At this point i was a bit more cautious and found myself a camping spot were i was well covered, called in my pred and got one kill. Got myself my harriers.

At this point i switched to my final class.

Class 5-

-ACR w/ Heartbeat and Silencer
-AA-12 w/ Silencer and Grip
-Bling Pro
-Cold-blooded Pro
-Ninja Pro

I sat back and let my harrier work this magic, using my heartbeat sensor i kept my area under watch and if i managed to single out an enemy i would move from my spot, say for instance i might have moved into the next room with him to kill him, this way he wouldn't see my camping spot on killcam and i could safely return. (Only do this if your harrier fails to get the kills needed, it's too risky)

My harrier then got me my AC-130 and i stayed with the class i had as it kept me well hidden. Im guessing you already have tactics for the AC-130 but i basically use the Large Turret at an area of enemies then keep going through the three different guns as they reload and gives me constant fire power.

I really hope this tutorial has helped you and if you need any help or advice my Gamertag is Hawaiiann Ryann, i will only reply to text messages though.