How do I counter Ostwinds (Rapid Fire!)

These fucking tanks are ruining the game for me. 90% of the enemy (and friendly to be fair) team seems to consist of these things, and they always manage to kill me while i bounce rounds off of them like pebbles. Is there a good place to aim or a giant weakspot or something, because at this rate I'm gonna give up on the 20 kills long before I get them