Steam Achievement/In-game challenge bug!

[irongod01]

This has been going on for a while now, but I haven't really felt it necessary to report it because it doesn't effect game play. The bug in question has to do with the weapon mastery achievements, and is better explained through an example than in general: Let's say that I finally get my first shotgun, and rank it up to rank 10. I earn Shotgun Proficiency 1, and get 1 of the 2 points needed to get Shotgun Mastery 1. However, once I get that same weapon to Rank 11, I get the 2nd point I need to get Shotgun Mastery 1, getting the in game challenge and the Steam Achievement, despite only having 1 shotgun. Although I haven't done this with shotguns in particular, I have gained Bow Mastery's 1 & 2, as well as Pole Weapon Mastery's 1 & 2 this way, when I shouldn't have them. When it happened with the Pole Weapon Mastery, ranks 11 and 21 gave me the second of three points for the achievements, and 12 and 22 gave me the third, so I believe that the bug is that the game only checks whether a weapon is above a certain level and of the specific type of weapon each time it ranks up, not whether or not the weapon has already been counted towards the achievement, as it should be.