User blog comment:Master Moridin/A (Potentially Unnecessary) Explanation for Inconsistent Ammo Count/@comment-26397825-20151107053015/@comment-26397825-20151107053814

It's called preloaded canisters, Phantom. The entire canister of the revolver could come out, and then she puts a new one filled with dust in.

Also, the dust in the first episode in the tubes on the wall looked solid too.