While a gun powder explosion in the cartridge seems instantaneous, if you slow it down you will actually find that each powder has a different “burn rate,” or speed at which it ignites. This is similar to how gasoline burns faster than lighter fluid. Gas burns quickly with a rapid explosion while lighter fluid burns slower and longer. The same effect can be found in different gun powders.

It should be noted that burn rate, does not have a standardized unit of measurement. In fact, burn rate is really only discussed in comparison to other powders; there is no universal yardstick. This makes burn rate a slightly controversial and highly-debated topics, as some reloaders feel that burn rate is less important or practically inconsequential.

Burn rate is important, however, when you are loading magnum vs. non-magnum rounds. Typically, a non-magnum load will use faster burning powders while a magnum cartridge will need slower burning powders. Magnum rounds need to generate greater power. Therefore, they use slower-burning powders, which creates peak pressure for a longer timeframe. This is also needed to give the heavier bullet maximum power and velocity.

Specifics will change by cartridge and bullet type, but in general a fast-burning powder is used for light bullets and low-speed pistols and shotguns. Medium-rate powders are used for magnum pistols, while high-velocity, large bore rifle cartridges will need slow powders, as they deliver the most overall power.

It might seem like an instantaneous explosion, but some powders burn faster than others and you should take this factor into consideration when reloading your cases.