Unverified. Ok, after you beat the three convicts in the jeep, you can re-spawn the jeep's gun by driving to another map (the maintenance tunnel map). When you load a new map, you reset the gun. However, you do not reset the damage done to the jeep, so dont hit too many zombies. You can have fun with the gun by driving back and fourth between the parking lot and the tunnels for Zombie Genocider.