User blog comment:Gundam Legilis/Volume 1 Weapons In Depth- Crocea Mors/@comment-3257939-20140617040651

Maybe it will be fixed with his semblance or since he doesn't know much about his own weapon (he didn't make it), there could be some sort of mechanism capable of making it a gun. It was in the "It's also a gun shirt" and as much as people keep saying it, NO, I really don't think they put Crocea Mors in the shirt as a joke.

I believe this weapon has another function and Jaune still has to find it. For example, Cardin's mace has a button and a gem which is connected to the mace, we can't give for sure that is only a mace given these traits and the fact that it hasn't been properly wielded since Cardin never used his mace at full strength.