I purchased the Delta Bundle and while I’m able to equip the Halberd on the vehicle, it won’t allow me to unlock any utility or ammo attachments. It keeps saying I must unlock the weapon to use. However, I was able to unlock the optics.
It's a bug so petition or /bug report will help but you will likely have to wait 1-3 patches. GM response from my petition: I'm sorry to have to let you know that it looks like there's a bug with the Utility and Ammo attachments on the new Halberd SE. The development team has been notified and we hope to have this corrected as soon as possible. Unfortunately, there is nothing that we can manually do to fix this for you in the meantime.
