M42 Contraereo is a very similar vehicle to the Wirbelwind, but M42 is a less maneuverable and agile vehicle than the Wirbelwind and also has much less ammunition to use than the Wirbelwin… to me this behavior seems that as always the developers have just unfairly nerfed Italy, for stupid reasons.
If you want it at BR 3.7 then you have to give it at least 2 more 640 round ammunition belts to use.
It is simply absurd that M42 has only 640 bullets, while the Wirbelwind has more than 3,200 bullets that can be used in battle.