Source: Starfinder Core Rulebook p.163
You have increased training in a particular weapon type, making it easier to hit your target.
Prerequisites: Proficiency with selected weapon type.
Benefit: Chose one weapon type (small arms, longarms, heavy weapons, etc.). You gain a +1 bonus to attack rolls with that weapon type. If your base attack bonus is at least 3 lower than your character level (or your mechanic’s class level, if you are a drone), you gain a +2 bonus instead.