A delivery device for semi-solid implantable material such as synthetic bone graft substitutes. The device comprises a handle (1), a cylinder (2) extending from the handle and having an outlet at its distal end. A piston (23) is operated by a trigger (5) and is slidable within the cylinder to displace the material from the cylinder. The cylinder has a substantially constant inner diameter along its entire length such that the outlet has substantially the same inner diameter as the rest of the cylinder. When the trigger is fully depressed, a ratchet mechanism (14, 32) is disengaged allowing the piston to be pulled back to a starting position.