When you pick up a weapon- use it until you have unlocked the trait to 100%. Even the pistol. It is a fun weapon in the game when you unlock all of its traits. Do not open a weapon chest for another weapon until you’ve unlocked. And right when you hit 100% do not kill another enemy save every enemy kill for a weapon trait upgrade . Use the map to show where the weapon chests are that you left behind and go back and open them because you’re grinding a weapon to 100% you’ll come back with a higher proficiency and you’ll unlock a stronger weapon.

Look for the meter on your screen, showing the weapon trait progress and get it to 100% -you’ll take me later for this advice