You can make an amendment based on two Addons ( links below ) ,,transport with working machine gun and Tau gun" and ,,stationary machine gun Alliance". This amendment will contain the following: the Alliance machine gun on maps half life 2 ( when you run through Garry's mod ) or use the spauner, you can take with you and shoot ( 400 rounds in stock, all in Mmod ), you can use the spauner to appear in front of you buggy ( well, or on the map Half life 2, when you run through Garry's mod ) to approach the wing, where the gun itself is fixed and, when you press E, remove it, shoot it as in Half life 1, and when you run out of bullets, again to approach the buggy, put the gun In place, it will be Charged and you can remove it again and shoot!