User blog comment:Gundam Legilis/Volume 1 Weapons In Depth- StormFlower/@comment-3146930-20140620003257

I also agree that this weapon is probably the worst for fighting the Grimm, but may be useful when fighting criminals in the city. Despite having a fast rate of fire, the bullets don't seem to do much against larger Grimm, seemingly jut brushing them off. Even when he was riding the tail of a Death Stalker and shooting at close range, the bullets still were not able to blast the stinger off.

However I imagine that these weapons may be designed for Grimm that are weaker, but travel in larger numbers. Beowolves would probably be annoyed by the bullets or they could injure them; same for the Ursa. Grimm like the Nevermore, Death Stalker, or the King Taijitu may be more rare. The blades on the other hand seem sharp enough to bypass Grimm armor, which makes me wonder why he didn't use them against the Death Stalker, but who knows.