User blog comment:Maki Kuronami/Lesson 28: Humanity did not receive a Grimm reminder/@comment-25091485-20141031105129/@comment-10380701-20141031233742

That is, if you're in the idea that Coco's bullets are strong, not her herself.

Weapons are the conduits for aura, and due to her experience, she likely has more powerful bullets in her gun thanks to her stronger aura. As Grimm are screwed over by both Aura and Dust, they shred like hot knife through butter against Coco.

If used against everything else? It may not have the same impact.

TL;DR Coco has a MASSIVE advantage against Grimm. But may not be that effective against fellow humans.