Burn Rate
How fast a propellant converts to gas, the property that must be matched to case size and bullet weight to build pressure safely and efficiently.
Burn rate describes how quickly a given smokeless powder combusts and releases its gas once the primer lights it. Fast powders finish burning early and suit small cases and light bullets, while slow powders meter their energy over a longer push and suit large, overbore cases driving heavy bullets. The goal is a powder that reaches peak pressure near the start of the bore and keeps the projectile accelerating until it clears the muzzle.
Burn rate is not a fixed number but a relative ranking, since temperature, pressure, and grain geometry all shift how a powder behaves in a specific chamber. Choosing a propellant whose burn rate fills the case well at a safe charge weight is the foundation of an efficient, consistent load, and a mismatch leaves velocity on the table or spikes pressure. Reloaders read published burn-rate charts as a starting map, then confirm real behavior at the range.