Injection device end of dose indicator

An injection device 100 comprising a syringe receiving body, and a firing mechanism 102 comprising a reaction component 114, which provides a reaction surface for a spring 112, that's located between a plunger 106 and the reaction component 114, to drive plunger 106 forward relative to the reaction component 114. Device 100 further comprising a locking mechanism for locking reaction component 114 in a first axial position within the body, the locking mechanism able to release reaction component 114 upon a predefined forward movement of plunger 106, thereby allowing reaction component 114 to be driven by the spring 112 in a rearward axial direction, until it impacts against a body component thereby emitting an audible indication of an end of dose. The locking mechanism may comprise a stop having a fixed axial position relative to the body, and a clutch 116 for rotating reaction component 114 upon the predefined plunger's forward movement to move reaction component 114 out of a blocking engagement with the stop feature, so allowing a rearward movement of reaction component 114, where the body component against which the reaction component 114 impacts may be a rear cap 104 fixed to a rear end of the body.