2 mechs one with arc 10 another with arc 12. 5 kills per round only means 35 matches. If combining with arc 6 remember to stop firing with arc 6 a second before they die. Bit of a grind but certainly doable. 

You don't need the upgrade weapon rank, enough points without it. 

KabiKabi, while the objective is indeed challenging, it's rather possible to complete it if you set your mind to receiving the 300 A-coins prize 🤗

https://link.plrm.zone/sdlgo/ebg0i

The arc torrent 12 is a p2w weapon

Yes, but how do you think you got the arc torrent 12. You also need to upgrade mech rank and that is too pricy just to get 300 acoins