Hi, I just started playing this game and I have no clue how the different weapon grades work in the shop. With the sniper weapons you have A, B, C and D. From what I get is that A doesnt have any stat buffs or nerfs, C is more of a reload speed thing but B and D are the same? Is there a difference between them? Or is that a bug? And what grade weapons would be preferably used? I'm a bit lost here.