Defiance Weapon Skills

Each individual weapon has its own experience bar which can be maxed out. This can be verified by accessing your character's inventory and selecting the specific weapon you would like to review. While your weapon is not maxed out, the experience gained for this specific weapon will also count towards your overall weapon skill experience. These weapon skill increases can unlock bonuses for the weapon type. Once the specific weapon experience has been maxed out, kills and actions done with this weapon will no longer count towards your overall weapon skill experience. All other experience gains for your character will still be gained normally.

Why would I keep an experience-capped weapon that is no longer providing additional skills for my character and this weapon type?

Once you have been able to gain max experience on a particular weapon, they can provide additional boosts which you may want to keep. With the weapon equipped and at max experience, any bonuses listed under this item when you select it in your inventory will be active and applied to your character.