User blog comment:DiegoAnime3000/The Manga adaptation is here!/@comment-25086632-20151117190820/@comment-24994749-20151117200706

Itwsort of hard to shoot a bullet without a propellant.

My guess is that a Dust core is used to enhance/add properties to the effect of the bullet and a more "from our world"/"less valuable" material is used as a propellant.