At this stage of assembly, the rimfire case is primed and ready for the loading of a propellant charge.
Charging with Propellant
Regardless of cartridge class, charging with propellant requires great control over the amount placed in each case. Too little propellant and the bullet may stick in the gun barrel; too much and the case could fail, injuring the shooter or damaging the firearm. This problem is compounded due to the small amount of propellant required for rimfire ammunition. Important factors to be considered when measuring rimfire charges are grain size and shape.
Propellants are metered by volume because there is no feasible method of weighing each charge while meeting production demands. Volumetric metering of granulated materials in a production environment requires the ability to produce consistent charges throughout the run. Various methods are used, depending on the loading equipment.
After charging, the cases are inspected for uniform propellant levels. This is the last point in production where it is possible to inspect for the presence of a charge.