(Note: This strategy only works in Battlefront I)
Spawn as a Rebel Vanguard or Wookiee Smuggler at a CP with 74-Z Speeder Bikes, then stealth yourself to the Shield Bunker. When you're there, enter the bunker and kill any enemies with your pistol or bowcaster and fire at the bunker using your rocket launcher, Thermal Detonators, or Time Bombs. After you're out of ammo leave the bunker and find a Ammo Droid (there will probably be enemy turrets). After gaining more ammo, continue the attack until you destroy the bunker. If the shield bunker is not destroyed by then, repeat the process.