A magazine well unit and a method are disclosed. The magazine well unit may have an upper portion having a firearm interface; a lower portion; a proximal portion; and a distal portion. The distal portion may have a magazine well to removably receive a box magazine. The magazine well may have at least one fore stop and at least one aft stop, the at least one fore stop and the at least one aft stop shaped to prevent the box magazine from passing beyond the upper portion of the magazine well unit. At least one of the fore stop or the aft stop may have an upper portion region having a surface for engaging the firearm.