Why is the Gauss rifle use small guns

I find that pretty strange honestly should go under energy weapons not small guns.

Any explanation for this? Is a mistake ?

The Gauss rifle only uses energy to propel the bullet. The target is hit by a bullet, not by energy. Hope this helps.

In all fallout games that had them, the gauss weapons fall in the small weapons - aboutthe only one that doesn’t is the gauss minigun (that’s a heavy). Quite logicla as they’re firing a material projectile and not and energy beam (with the same recoil, projectiel drop and travel time as regular guns - though the last two are mitigated by the higher projectile speed)