6v6 comp puts me in diamond when I am silver

okay so I have only been playing shooter games for as long as OW2 has been out. it was my first and mostly only shooter game. Recently I have been getting more and more into comp. in regular role q comp I am silver 1, but when comp 6v6 came out and I got my placements it ended up putting me in diamond. I have played a few games and I hvae been able to consistantly been able to stay in diamond (usually around diamond 2-3 range) I don't think I belong in diamond especially since I am unable to climb out of silver in 5v5. is the rank system just messed up or something?