Are you tried finding these balls for years?! I have simply solution to this.

Balls locations:

1. Under flak cannon
2. Top of the main Bunker
3. Top of the scorestreak tower

video how to get those places: https://www.youtube.com/watch?v=KCCJNpCLzyk

if its too hard send me a message or commend on my profile, i can make it to you:)!
Thank you and love,
Kasaldo