I'm not really sure what to say about this gun. Many people tell me it's a "safety over damage" type of weapon, but the limited mobility it gives you isn't much on the "safety" side. And its overall dps is terrible compared to stuff like Alchemers, Autoguns, and Antiguas.
Plus the charge attack sucks.
Its Piercing-damage advantages really ends up being what makes it worthwhile, compared to the Iron Slug. The overall series could see a base damage increase; as comparison, each hit from a Needle Shot charge deals more than a Magnus shot of equal * level. Otherwise, the inspector is generally fine and players use it.