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How does the grain size of black powder affect its burning rate?
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Because the burning of black powder is a surface phenomenon, its burning rate is directly influenced by the amount of surface area exposed to combustion.12
- Fine granulation: These grains have a larger total surface area relative to their volume, which causes them to burn faster.12
- Coarse granulation: These grains have less surface area exposed to combustion, resulting in a slower burning rate.13
Historically, this relationship was used to control the performance of gunpowder in firearms. While fine powder burns rapidly, it can create excessive pressure in a gun barrel; therefore, manufacturers began producing larger, uniform grains to slow the burning rate and improve safety and ballistic performance. By adjusting the size of the granules, the speed of combustion can be precisely varied for different applications.23