Andrew,
If it is a cartridge, it is subject to the Federal Excise Tax for ammunition and Federal Regulation. The propellant doesn't matter.
If it is a modern manufactured Cartridge Weapon it is subject to Federal Excise Tax and regulation. If a particular weapon was produced before 1899, it is considered an antique and is exempt from most of the Federal laws concerning firearms whether it uses a cartridge or not. This is talking about a true antique, not a reproduction in the case of cartridge guns. This includes transportation, license requirements for receipt or commercial sale and so forth. These are just Federal Laws, most States, Municipalities and local governmental entities consider even muzzle loaders as weapons, but the regulation of the sale transport etc. varies.
For instance you can legally carry a Cap and Ball Revolver in many places, in fact in many states a convicted felon can own a C&B revolver; but, you can't carry a night stick or a club. You also can't carry a black jack, brass knuckles or a spring opening knife. Those all come under the heading weapons prohibited for carry even though a C&B revolver is obviously a more effective weapon.
So to get back to your question, the components you listed are not subject to Federal Excise Tax on ammo and firearms. The Pittman-Robertson Act only applies to assembled ammunition and it does not differentiate propellants, it is on the price as sold of the assembly.
The Federal government does not differentiate fixed ammunition cartridges by propellant, except for transportation of hazardous materials. Muzzle loaders and black powder weapons that do not fire "fixed ammunition" such as reproduction breech loading paper cartridge Sharps rifles are not considered "firearms" under the Pittman-Robertson Act.
I hope this helps.
~Mako
