This series is to demonstrate how to properly and fully dismantle, clean, lubricate, and reassemble an automatic gas-operated shotgun. For this example, I will be using a Remington 1100 model, which is basically just the older version of the Remington 1187. If you are using a different model or brand, please use discretion with specifics; not all details may be the same.
I should also mention that this gun is already fairly clean, but it is always good to make sure your gun is clean even if it hasn't been used much since the last time you cleaned it.
Step 1: Collect Your Materials
In order to properly clean a shotgun, you will need a few basic items.
A bottle of solvent. I used Hoppe's Number 9 Solvent.
A bottle of gun oil, such as the small bottle of Rem Oil I used.
I also used a can of Molly Lube Dry Film Lubricant, a spray bottle of Hoppe's Elite Gun Cleaner, and a bottle of Break Free Cleaner, Lubricant, and Preservative.
You will also need a greasy rag, a nylon brush (a toothbrush will also work), cleaning pads, toothpicks, needle-nose pliers, masking tape, a hammer, a rolled up towel or other stable base object, a surface you don't mind ruining and that nothing can soak through, and a barrel cleaning rod and attachable wire brush and mop-tip. The Q-Tips, a small screw driver, and silicon rag are optional, but could be useful.
Step 2: Make Sure Your Gun Is Safe
Always, always, always before handling your firearm in any fashion other than actually shooting, make sure, by visual and physical inspection, that there are no rounds in the chamber or magazine and that the safety is on. By doing this, you ensure that the gun will not accidentally discharge a round you may have forgotten, or did not know was loaded.
To do this with a Remington 1100, simply pull back on the firing pin handle until it locks in place, and push the safety button so that the side with the red band is hidden.
Step 3: Take Off the Magazine Cover
First, unscrew the cap on the front end of the magazine cover, or forearm. Once it is fully unscrewed, slide the forearm forward until it is completely removed.
Step 4: Remove the Barrel
Once the forearm is removed, firmly grasp the barrel and pull forward and slide it off of the receiver.
On another note, if you wanted to simply change out your barrel, this is as far as you need to go. Simply replace your barrel after this step and reassemble your shotgun in reverse order from how you disassembled it.
Step 5: Remove the Piston, Piston Seal, and Barrel Seal
Once the barrel is removed, you should see three separate rings; two metal and one plastic. Remove each one at a time and neatly place them aside. Make sure to note their order and which direction they are facing.
In order to protect the plastic barrel seal, you may want to wrap some tape (I used masking tape) around the threads at the end of the magazine. The plastic barrel seal is one of the most fragile, yet important parts of the gun.
Also, wipe down the magazine end with a greasy rag (or in my case, a silicon cloth) as grime and dust may have built up along it.
Step 6: Remove the Bolt and Action Bar Assembly
Next, you'll want to remove the bolt handle. To do this, carefully, and slowly release the action by pressing the release button on the bottom of the gun and easing the bolt to the closed position. Then, gently pull the bolt handle free from the bolt.
Once this is done, push the release button and raise the carrier on the bottom of the gun to reveal the feed latch. Press this against the wall of the gun, and simultaneously gently pull the action assembly forward and slide it off of the magazine. The bolt should easily come free of the action bar assembly once removed.
Step 7: Detach the Trigger Assembly
In order to detach the trigger assembly, you must first remove the two pins holding it in. To do this, I propped the gun up so that the butt of the gun was laying on the table and a rolled up towel was placed under the base of the magazine. Then, I used a hammer and a thin piece of wood to gently tap the pins out of the gun, until they were able to be pulled free from the other side.
Once the pins are removed, simply pull down on the trigger guard to remove the assembly from the receiver.
Step 8: Remove the Spring Link
To remove the link, use a pair of needle-nose pliers to pinch the link closed and pull if forward until it drops free. Be careful not to be rough on the gun metal with the pliers so as not to damage the metal. Then, rotate the link 90 degrees so that it may be removed from the receiver.
Once the link is removed, the gun is completely stripped, and ready to clean.
Step 9: Cleaning the Barrel
The first part I usually clean is the barrel. To do this, soak a cleaning pad in your solvent, squeeze it so that it is not dripping, and push it through the barrel using your cleaning rod. Let the solvent sit for about 10 minutes.
WARNING: This solvent, and many others, are extremely flammable. Do not allow it near any sources of electricity or fire, and try not to let it drip on anything. It may ruin or damage anything it sits on for very long, including skin. I used a board and old towel to keep the solvent from dripping on my table.
After letting it soak, push the rod with the metal brush attached back and forth within the length of the barrel to loosen any built up grime. Then, use either a mop-tip or a dry cleaning pad at the end of the rod to wipe out the loosened crud. The last step should be repeated until the inside of the barrel shows no dirt clumps or specks, as shown.
Also, you should use a few drops of solvent and a cleaning pad or Q-Tip to clean the open base end of the barrel. You may want to use a nylon brush to get the larger clumps off, but be careful not to scrub too hard, or you'll wear away the metal.
Make sure to check the gas cylinder (the ring attached to the barrel that goes around the magazine and action) for any grime build-up as well. Use solvent and a cleaning pad or nylon brush to clean it out. Check the gas holes (two small holes inside the gas cylinder) to make sure they are not clogged, and use a thin wire or tooth pick to unclog them, if they are.
Step 10: Clean the Barrel Seal, Piston, and Piston Seal
For the barrel seal, avoid using solvent, as it may be harmful to the soft plastic. Instead, simply wipe it down with a cleaning pad. This is a very delicate piece, so check it for cracks or tears. It is usually a cheap and smart move to have a few extra on hand, as broken barrel seals are a common, crippling problem for a shotgun.
For the piston and piston seal, I use a cleaning pad and solvent to wipe them down until no grime or black stuff shows up on the pad. Depending on how frequently they are cleaned, and how much grime has built up on them, you could also soak them in solvent or Carbon Killer to loosen the dirt before wiping them down.
However you clean them, make sure the piston and piston seals are dry before replacing them on the action, as leftover solvent may be left on the metal where the barrel seal rests, and this may be damaging to it.
Step 11: Clean the Trigger Assembly
Remington suggests not disassembling the trigger assembly, and rightfully so as it is not necessary.
Simply spray or manually apply gun cleaner (or Rem Oil) to the entire assembly and let it sit.
Make sure to shake or wipe off any drips of excess cleaner/oil.
Step 12: Clean the Action Assembly, Bolt, and Inside of the Receiver
To clean the bolt, apply a small amount of cleaner to a cleaning pad or Q-Tip and rub any built up grime off of all surfaces of the bolt. The outer surface will typically not need to be wiped, but make sure it is clean.
Then, apply cleaner to the action assembly in a similar manner, focusing cleaning efforts on the part the connects to the bolt.
Do this with the inside of the receiver as well, spreading the cleaner with a nylon brush, and wipe down all inner surfaces with a greasy rag until no grime can be seen.
Step 13: Lubricate
Lubricating key parts of a shotgun is also very important. It ensures that the moving parts of the gun do not stick and that it fires smoothly.
This being said, the most important places to lubricate are the receiver rails (shown above) and the action. These are the two places that experience the most friction.
I simply put two drops at the end of each receiver rail and let them drip down along the inside of the receiver (I am pointing along the rail to show this).
Then, I used the Molly Lube Dry Lubricant and applied a very thin coat along the length of the action and magazine.
Step 14: Reassembly: Link
In the same way that it was removed, replace the spring link by aligning the T end of the link within the receiver, and then pinching the link together and inserting it into place with needle-nosed pliers. Once in place, check to make sure that you can push on the link and it can push back on the spring and then move back into place.
Replaced correctly, it should look like the second picture.
Step 15: Reassembly: Trigger Assembly
To replace the trigger assembly, first insert the assembly into the receiver and align the two pin holes so that you can see through them.
Then, push each pin back into their respective holes. You may need to use the hammer and piece of wood to get them back into place, but be sure to be careful and gentle when using the hammer. Make sure the pins are flush with the outside walls of the receiver on both sides.
Step 16: Reassembly: Bolt and Action Assembly
First, place the bolt back on the action assembly, with the tapered end pointing toward the stock.
Then, push up on the release button, raise the carrier on the bottom of the gun, and hold down the feed latch (as shown) to push the action bar assembly back fully. Once these are in place, replace the bolt handle.
If everything is replace correctly, you should be able to smoothly pull back and lock the bolt and then release it with the release button.
Step 17: Reassembly: Piston, Piston Seal, Barrel Seal, Barrel, and Forearm
First, the two metal rings and one plastic ring need to be replaced on the action. Slide them over the end of the magazine and down the action until they are flush with the ring of the action bar assembly when the bolt is closed (position as shown).
Make sure to note the orientation and order of the rings. With the gun pointing to the right, the order from left to right is Piston, Piston Seal, Barrel Seal.
The tapered edge of the piston seal should form-fit into one side of the piston. The barrel seal should end up resting in a groove in the metal of the action.
Once all of the rings are in place, slide the barrel back over the action until it stops. It should be covering the barrel seal.
Once the barrel is in place, slide the forearm back over the magazine and finish by screwing the cap back onto the end. The cap should click as it turns once it gets close to being tight enough. Tighten snugly, but it does not need to be extremely tight.
Step 18: Final Wipe Down
The last step is to use a lightly oiled rag (using the Rem Oil) and rub down all outer metal surfaces of the gun. A very thin layer is all that is needed to prevent rust pockets from forming.
I used my silicon cloth which has silicon oil already in it to wipe my 1100 down, but you can use the rag mentioned above if you do not have one of these.
This last wipe down is important because the oil and salt from your skin on the metal can degrade it and will eventually form spots of rust.
Step 19: Finished!
Assuming you've followed all of the previous steps, your shotgun is now clean and ready to fire!