Here's something Witch I find interesting. A normal .50 bmg cartridge has volume for the powder about 20ml. The smokeless powder is about 15g witch at 6000joules/gram is 90 000 joules of total released energy, about 20 000 of witch become muzzle energy. A 20ml case can hold organic nitrate compounds(similar to smokeless powder and nitroglycerin) with about 200 000 joules. Problem-making it detonation resistant as the smokeless is more difficult. The same 20ml case can hold about 400 000 joules of metal powder enhanced propellant(like in rockets). Problem-heavy barrel erosion due to the high temperatures. The question is, why humanity is still bothering with these low energy density fuels. The high energy density will allow for carrying much more rounds. Each shot to be cheaper, less brass, less transport costs. The chamber will be with less inner diameter and will have thicker walls for the same size. High energies will be possible without bottle neck.