I have tried doing this challenge several times through Battle Royale. I have gotten so many weapons to fully max training meaning they are purple guns but were white common guns from ground pick up and the progression does not count toward this challenge please help!
The training path is for your operator not your weapon. On the right side of your screen you should see some white opaque boxes with a bar on the side of them. As you complete missions or get kills and assists that bar will move up. As you reach a new box you gain a new perk. Once you reach the max that is when it should apply to this challenge. Sadly the challenge is bugged and even doing that it still does not apply.
