I remember Helen ordering people to refrain from using 'aether' weapons. Which I think applies to the forearm weapons. But, she seems to be using the sword and a similar type of gun herself. She did mention using any means necessary to keep that door open, as well.
If I've misjudged this weapon, and it's something my character would know, please let me know so I can edit that post. I tried to do my research, but since this is the first time I've fired anything, I'm somewhat cautious.