A drug delivery device adapted to receive a cartridge and hold it in a mounted position is provided, comprising a housing, an expelling assembly, and a front-loaded cartridge holder assembly adapted to receive and hold a cartridge in a mounted state. The assembly comprises cartridge holding means actuatable between a receiving state and a holding state, as well as a user operated actuation sleeve being rotationally actuatable relative to the housing between a loading state and an operational state, such that the cartridge holding means is actuated from the receiving state to the holding state when the actuation sleeve is actuated from the loading state to the operational state. The actuation sleeve is configured to enclose at least a portion of a mounted cartridge and is provided with inspection means allowing at least a portion of an enclosed cartridge portion to be visually inspected.
