Speed loaders and assemblies for loading cartridges in revolver cylinders are provided. A speed loader assembly for loading cartridges in a revolver cylinder includes a speed loader, the speed loader including a body which defines a plurality of passages, each of the plurality of passages configured to accommodate a cartridge therein. The speed loader assembly further includes a protective casing removably connectable to the speed loader, the casing including a sidewall defining an interior and having a closed polygonal cross-sectional profile. Portions of cartridges extending from the passages are encased by the protective casing.