Proper selection of gunpowder is important for any realoading application. The various characteristics of the powder will influence the ballistics of the completed round, the consistency of metering, and many other things. In order to select a powder for your application, it’s important to understand the various characteristics that different powders exibit.
There are a few characteristics that are most important to consider when choosing a powder:
The burn rate of the powder will greatly affect the peak pressure generated by the powder charge, and is important to match to the type of load (standard -vs- magnum), the bullet weight, and other factors. Typically, non-magnum loads utilize faster burning powders, where magnum loads utlilize slower burning powders.
The density of the powder will determine how much bulk there is for a given charge weight. Bulkier powders can be helpful to prevent double charges (if one charge takes up most of the powder space, a double charge will either overflow, or not allow the bullet to seat, halting the ram before it reaches the top).
Each gunpowder particle is called a granule. The shape of the granules are a part of how the powder is manufactured, and will impact burning characteristics, and metering. The following is a list of common powder granule shapes.
This type of powder consists of spherical granules that are typically small in size. This type of powder usually meters well.
Flattened ball powder
This powder is very similar to ball powder but is flattened slightly. This type of powder behaves almost identically to ball powder.
This powder has granules that are shaped liky tiny disks. Flake powder can be more difficult to meter correctly due to the fact that it can “stack up” in the powder measure, and can be less uniform in density when metering.
This type of powder is most frequently used in rifle applications. Stick powder has granules that are shaped like small extruded cylinders. One issue that can arise with stick powders is the powder measuring cutting the sticks.
Some common powders, from left: Winchester W-231 (flattened ball), Winchester W-296 (ball), Alliant Blue Dot (flake), Alliant Unique (flake)