Just luck? Or an acctual rule to looting

I don't know about you, but when I get my first famed of weapon its the worst one and I get the next best thing. For example, when I got my first set of famed throwing knives, it was vipers den, then amazon, then swamp, then shark fang, then two hawk idol, then assassins, and most recently a set of bayou knives. I think that the next famed knives i will get will be demon fang, then golden idol, and lastly silver freeze. Is their programing in the game that makes looting this way? Am I just weird? Same thing happens with my sword and gun! Leave some comments below if the same sort of thing happened to YOU.