A transport for a rectangular tape cartridge enclosing a supply reel having a web of magnetic tape wound thereabout terminating in a free end attached to a leader block. The illustrated embodiment of the transport is designed to fit within the computer industry standard 51/4-inch form factor and utilizes the 1/2-inch tape cartridge defined in Proposed American National Standard X3B5/85-075. An elongate rectangular housing has internal mechanisms for supporting the tape cartridge therein and referencing the cartridge off its side surfaces. The cartridge is manually inserted into the housing through a slot in a face panel extending across a transverse end of the housing. Electro-mechanical assemblies lock the cartridge in place and complete the loading sequence by engaging a drive chuck with the hub of the supply reel, extracting the leader block from the cartridge, and pulling the leader block to the take-up hub to thread the tape along a tape path. A gear driven articulated arm has an outer end which is guided along a hook-shaped track and carries the leader block into engagement with a receptacle in the take-up hub. Precision transverse movement of a magnetic head in the tape path is accomplished by a stepper motor coupled to a band drive through a worm gear reduction.