Originally Posted by
Xazur
There is weapon exp, and weapon skill exp. Weapon exp = the bar displayed on the weapon. Weapon skill exp = the level of your weapon proficiency which gives you bonus stats for using that kind of weapon. When you select a weapon it will tell you which category that weapon is part off so all the weapon exp you get all goes towards that same proficiency. The weapon exp is based on the amount of damage you deal to the enemy, so higher damage weapons do max out the fastest.
So this is how it goes: Damage dealt -> Weapon exp bar -> Weapon skill profiency