Maybe it's my fault, but I dont understand fully the Micro weapon upgrade. Is it possible to apply this upgrade for a heavy weapon, like the MP Lascannon in the Core book?

Thanks a lot

No, read the last sentence in the Micro upgrade's description:

Upgrades: Any Pistol or Basic Las, Solid Projectile, Flame, Bolt or Plasma weapon.

The "Pistol or Basic" bit is the key section - that's what sized weapons it can be applied to. Even though it lists Las weapons among the types, a Man-Portable Lascannon is a Heavy weapon, not a Pistol or Basic.

It's clear now.

THX