Borderlands: Game of the Year Edition
81 Achievements
64-76h
Weapon Aficionado
Reached proficiency level 10 with any weapon type
44.1%
How to unlock the Weapon Aficionado achievement in Borderlands: Game of the Year Edition - Definitive Guide
The weapon proficiency progress can be viewed in the menu.
If you do have a friend who is a higher level than you, jump into their game with your weapon class equipped and have them kill higher level enemies, the weapon proficiency will quickly climb without needing much work from yourself.
To do this naturally, you'll have to stick to one type of weapon (Assault Rifle, SMG, Pistol, Sniper etc). As you kill enemies, your weapon proficiency with that weapon type will begin to rise. If you stick to one type of weapon, the trophy will unlock on your way to reaching level 50.
You can also unlock this quite easily if you join a high-level friends game. Let your friend do all the shooting, and all you will need to do is stand back and watch the weapon proficiency level of whichever gun you have equipped climb pretty quickly. In under an hour using this method, you will unlock the trophy.
You gain proficiency with weapons simply by using them to kill enemies. Each character has weapons that suit their playstyle and will typically have skills and character mods that complement those specific weapons, though you can use any weapon with any character to unlock this.
This will come with natural play as long as you stick to the same weapon for a majority of the time you're playing your initial playthrough. Try to only change the weapon for an upgraded version and not for a different weapon altogether, at least until you have unlocked this achievement.
You gain proficiency levels by killing enemies. Every time you kill an enemy, you will gain a small amount of experience towards the proficiency of the weapon you're using so the more you use a particular weapon, the quicker you will level up its proficiency. You will probably want to use the weapon that suits your class, this will also benefit you because of the skills you have and the extra levels will add bonus damage and much more thus helping you out later in the game. You cannot earn proficiency with Grenades or Melee attacks. Note: You can also earn this trophy is in Co-Op (credit to Lurkki91 for this info).