Board Thread:Speculation House/@comment-69.66.169.227-20130802171349/@comment-749367-20130907172441

The only character shown to actually fire any kind of solid projectile is Nora, who fires pink heart-tipped grenades. I think it does make some sense that the other characters are firing energy projectiles of some kind, seeing as they seem to consume large amounts of ammunition without any need to reload (especially in Episode 8, in which Yang fires an extremely large number of shots without changing her ammo once throughout the episode).

At the same time, however, we see Ruby dropping spent shells occasionally, so she may be using bullets as well.