A couple things here I see as common misconceptions. I am what some would call a "gun guy" and one who also reloads a list of calibers. Ammo is not considered an explosive nor is smokeless powder. Black powder is considered an explosive but modern "smokeless" powder is a "rapidly burning compound." In other words a pour a pile of black powder on the ground and throw a match on it and you will have an explosion. Do the same with smokeless powder and it will burn very fast but no explosion. Smokeless powder develops it's power from the expanding gasses being trapped inside the case and chamber of the firearm.
Also; I can't quote the exact law on this but do know there is a legal difference between a manufacturer or retail seller of ammo being able to ship their product and an individual trying to ship the same ammo. In other words I can buy ammo and have it shipped to me; depending on state and local ordinances. But it is illegal for me to re-package and ship that same ammo. Also, don't even think about trying to get around the law by labeling it as something else to ship, way illegal. Hope this helps, Jim.