There's no bugged weapons, you simple NEED the third sniper rifle because it's the only one which can use bullets caliber .338. Buy that and ignore the others because you need it to end the game. I hope this can be useful for those wondering how get the medium achivement.
 "Tactical Assassin 2"){kind=icon}
 "Dillo Hills"){kind=icon}
 "CycloManiacs"){kind=icon}
 "Upgrade Complete 2"){kind=icon}
 "Idle Quest"){kind=icon}