Apparatus and associated methods relate to a firearm speed loader comprising (a) an elongated tube assembly for holding one or more ammunition cartridges in a central lumen defined by a wall of the tube assembly and (b) an elongated aperture formed in the wall of the tube assembly. In an illustrative example, two grooves may be formed into the wall distal to a proximal end of the tube assembly. One or more cartridges may be inserted into the central lumen by aligning the rim of each cartridge with the grooves. A user may place a digit of a hand into the central lumen and urge the cartridges from the proximal end to a distal end of the tube assembly, thereby causing the cartridges to be pushed from the tube assembly into the firearm. Various embodiments may advantageously reduce a time necessary to reload a firearm magazine.