Propellent Burning Rate
Q: I know that there are two basic types of rifle powder, single- base and double-base, but little else. Can you tell me the difference between single and double base powders and what is done to vary their burning rate? I've just set out to reload my cartridges and would like to learn a little about propellant powders.
A: Single-base powder has only one component, nitrocellulose, whereas double-base powders have two - nitrocellulose and nitroglycerine. The latter has the most energy. The size and shape of the powder granule, whether it is porous or solid and the application of various deterrant coatings govern burning rate. Winchester double-base Ball powders are harder to ignite than other types, due to their having heavier deterrant coatings and lower flame temperatures. They are best sparked off using magnum primers. Most powders have a pressure range at which they burn best. If that level isn't reached, you get even more unburned powder than normal, higher velocity spreads and sooty cases.