Just found a glitch where you can equip attachments you don’t have unlocked yet to your zombies build. All you need to do is have a zombies build preset, and then go into multiplayer and create a custom match. In the pregame lobby you can go into your custom classes and see which guns have a zombies build. Edit the zombies build and add whatever attachments you want since it’s a custom match everything is unlocked. When you start a game of zombies and grab the gun it will have all the attachments you put on it. I’ve been grinding the asg shotgun in zombies and I was able to put the rapid fire mod and drum mag on it even tho I only have the gun to like lvl 20. Hope this helps with the camp grind.