An injection device comprising: a body for receiving a syringe; a firing mechanism comprising a reaction component, a plunger configured to be axially displaced in a forward direction relative to the reaction component, and a drive spring located between the reaction component and the plunger for driving the plunger forwards upon activation of the injection device, wherein said reaction component provides a reaction surface for the drive spring; and a locking mechanism for locking the reaction component in a first axial position within the body, the locking mechanism being configured to release the reaction component upon a predefined forward movement of the plunger thereby allowing the reaction component to be driven in a rearward axial direction by the drive spring until it impacts against said body or a component secured to the body to thereby emit an audible indication of an end of dose, characterised in that said locking mechanism comprises a stop feature having a fixed axial position relative to said body, and a feature for causing a rotation of the reaction component within the body, substantially upon said predefined forward movement of the plunger, to move the reaction component out of a blocking engagement with said stop feature and thereby allow rearward movement of the reaction component, wherein said feature for causing a rotation of the reaction component within the body comprises a clutch having a substantially fixed axial position, the clutch being rotatable within the body by axial movement of the plunger towards the end of a delivery stroke to thereby cause said rotation of the reaction component. a body for receiving a syringe; a firing mechanism comprising a reaction component, a plunger configured to be axially displaced in a forward direction relative to the reaction component, and a drive spring located between the reaction component and the plunger for driving the plunger forwards upon activation of the injection device, wherein said reaction component provides a reaction surface for the drive spring; and a locking mechanism for locking the reaction component in a first axial position within the body, the locking mechanism being configured to release the reaction component upon a predefined forward movement of the plunger thereby allowing the reaction component to be driven in a rearward axial direction by the drive spring until it impacts against said body or a component secured to the body to thereby emit an audible indication of an end of dose, characterised in that said locking mechanism comprises a stop feature having a fixed axial position relative to said body, and a feature for causing a rotation of the reaction component within the body, substantially upon said predefined forward movement of the plunger, to move the reaction component out of a blocking engagement with said stop feature and thereby allow rearward movement of the reaction component, wherein said feature for causing a rotation of the reaction component within the body comprises a clutch having a substantially fixed axial position, the clutch being rotatable within the body by axial movement of the plunger towards the end of a delivery stroke to thereby cause said rotation of the reaction component.