It seems like each weapon type can fully reload in a fixed time, so number of bullets loaded per second varies with magazine size. When slotted into a pair of boots, these mods will steadily reload stowed weapons of a certain type over time, a bit like a slower but general-purpose version of the Auto-Loading Holster weapon perk. With Season of the Lost in Destiny 2, Bungie has introduced Holster mods for leg armor.
