Disclosed herein are wearable drug delivery devices and methods for component positioning of a linear shuttle pump. In some approaches, a pump may include a pump chamber operably coupled with a piston, and a detent apparatus, wherein the detent apparatus comprises a detent body, a detent arm, and a detent engagement member. The detent engagement member may be retained in direct physical contact with first or second arrest locations of either the detent body or the detent arm. The pump may further include a piston grip coupled to the piston, the piston grip including a grip component engaged with an exterior of the piston. Movement of the piston grip may cause the piston to move axially relative to the pump chamber to control receipt and delivery of a liquid drug.