Captain Lawgof is south of the Coal Trucks. Talk to him, agree to help him repair the fence, and he will give you six railings.
You will automatically have a hammer in your toolbelt
The damaged railings around the complex are bent; repair these by "inspecting" the appropriate sections of railing. Some bent railings are difficult to find (just look at the bottom of the bars of the fence. The six bars that need fixing will not be straight lines, making them stand out from the rest of the straight bars). It may help to adjust the camera angle so that it is viewing the fence. If you fail to repair a rail, you may take 10 or 20 life points or your strength or crafting may be temporarily reduced. Whether you fail or succeed is purely random.
Return to Captain Lawgof. He will explain that communications with the watchtower have stopped. Head south. Just outside the gate there is a ladder on a hill surrounded by several wooden stacks, this is the watchtower. Go up two ladders and in the far west corner of the second room take the Dwarf remains in the corner of the room on the top floor then head back to Captain Lawgof and speak to him. If you don't completely finish your conversation with Captain Lawgof, the dwarf remains will not appear.
Captain Lawgof will identify the remains of Gilob, who had a son named Lollk. He is missing, and Lawgof will ask that you find him.
Head south-east to a cave. You will have to walk around the Fishing guild to find the entrance.
Once inside the cave, it will fork into three passages. Take the west passage to find a goblin outpost. Go to the furthest room from the entrance (this is the room that is west/left of the room that has two goblins guarding a flight of stairs going downward). Look in the north-east corner, as you will need to search the crates (it is the northernmost box of the seven boxes against the east wall of this room) to find Lollk. Talk to him and he will thank you. Return to Captain Lawgof.
Captain Lawgof will ask you to fix his broken multicannon. Use the toolkit he gives you on the cannon. You will need to match up three tools with the three parts on the screen that shows up. These must be done in order!
Use the hooked tool on the spring.
Use the pliers on the safety switch at the bottom.
Use the tooth tool on the gear located at the bottom of the hammer.
Talk to Captain Lawgof again. He will tell you that he doesn't know how to get ammo for the cannon. He will ask you to go to the Dwarven Mines outpost south of Ice Mountain to find out about the ammo. (You can use home tele, You must have the lodestone activated) You must complete this entire conversation or you will not be able to open the door and talk to the engineer when you reach the mining camp.
Or can use home tele to Lumbridge (standard spellbook) and outside there use the canoe (transportation) to Barbarian village.
An even faster path is via using home tele to Edgeville. It brings you within 30 seconds of Nulodion.
Go to the Dwarven Mines outpost (North-east of Falador's northern entrance, North-west of Gunnarsgrunn) and talk to Dwarf Engineer Nulodion, just outside the mine entrance(in the western of the two buildings by the entrance to the Dwarven Mine. If you are unable to open the door to speak with him, return to Captain Lawgof and complete your unfinished conversation. Nulodion will give you an ammo mould and some instructions. If in the future, whenever you need an ammo mould, you can speak to him and receive one for free if you do not already have one in your inventory. In addition, it can be purchased. The drop trick can also be used if you don't want to go back to him to get another ammo mould after the quest.
Finally, go back to Captain Lawgof and talk to him. Quest complete! Note: if you are interrupted in the middle of the conversation he will take the mould but you will not finish the quest.