Nice alfa strike, decent DPS and mediocre crit chance compared to other piranhas. Compared to the PIR-1 meta (3xcHSL, 12xcMG) this build has more emphasis on the alfa strike and, consequently, needs more cooling (+1 DHS), so this build has a better chance to open the back of a mech (even if you can't focus a component properly) but halved MGs DPS and overall crit damage. If you don't mind having additional armor on arms (IMHO you should, since they can soak up damage and maybe even save you once from pinpoint weapons), strip them and add another half ton of ammo.
OP mech is OP 1100 damage on Caustic Valley and around 30 skillpoints spent only in firepower and ammo. Spoiler: Screenshots
2 tons of ammo for 6 HMGs are few: it's only 48 seconds of dakka dakka, even with max ammo skills. By stripping some armor you can fit another half ton of ammo, so you will be able to reach to 1 minute of dakka.
