The indirect fire device for fixing fasteners (13) in a substrate material of the invention comprises a piston for driving a fastener (13) movably mounted in a barrel and a plug guide (11) for guiding a fastener (13) towards the substrate material. The device is adapted to receive a magazine (19) for receiving a strip (14) of fasteners (13) in order to introduce the fasteners (13) one by one into the plug guide (11). Each fastener (13) is held in a sleeve comprising bridges (16) for connection to another sleeve (15). The plug guide (11) of the device includes a zone having an enlarged circular section (21) at the opening of the magazine (19) leading into the plug guide (11), extending axially over the length (h) of a sleeve (15) increased by the stroke of the plug guide (11) for loading the device (L-L′).