This post is based on a chapter from the Remington 870 Guide eBook.

The Remington 870 is easy to disassemble and reassemble; you will only need these instructions the first few times. With enough practice, you will be able to disassemble and reassemble your shotgun with your eyes closed.

You may need to disassemble your shotgun in the following cases:

• For the first cleaning of your Remington 870, due to the preservation grease, right after purchase.
• For regular cleaning and maintenance of your shotgun.
• When checking your shotgun’s barrel to see if there are any obstructions inside.
• For transportation of a shotgun, disassembled in a case or small bag.
• For storage of a shotgun, disassembled in a case or small safe.
Disassembly
Never forget about the safety rules when disassembling a shotgun. There are known cases when carelessness during the disassembly of a gun was the cause of accidents.
WARNING! Check the ejection port, chamber, and magazine tube to make sure that there are no shells in the shotgun prior to disassembly.
1. Engage the safety.
2. Push the action bar lock upward and pull the forend back to open the action.
Slide the forend back, approximately halfway.

Remington 870 Disassembly and Reassembly

Remington 870 Disassembly and Reassembly

3. Unscrew and remove the magazine cap (magazine extension).
If you have a magazine cap, the spring is held in place by a magazine spring retainer; if you have a magazine extension, the spring is held by the extension itself, and will fly away when the extension is removed. Be careful to hold the magazine extension firmly and decompress the magazine spring slowly.

Attention! Magazine springs are under pressure; wear eye protection

Remington 870 Disassembly and Reassembly

Remington 870 Disassembly and Reassembly

Remington 870 Disassembly and Reassembly

Remington 870 Disassembly and Reassembly

4. Take out the magazine spring retainer, magazine spring and follower.

Remington 870 Disassembly and Reassembly

Remington 870 Disassembly and Reassembly

5. Pull the barrel from the receiver.

Remington 870 Disassembly and Reassembly

Remington 870 Disassembly and Reassembly

6. Compress and hold the left shell latch.

Remington 870 Disassembly and Reassembly

Remington 870 Disassembly and Reassembly

7. Slide the forend forward and off the magazine tube. Hold the bolt and the bolt carrier, because they will fall off from the action bars.
8. Take out the bolt and bolt carrier from the rear of the action bars.
9. This step is for the Remington 870 that doesn’t have a magazine extension, with the spring kept in place by the magazine spring retainer.
Attention! The magazine spring is under pressure; wear eye protection.
Insert a flat head screwdriver into the slot in the magazine spring retainer. Push the magazine spring retainer into the magazine tube and rotate it. This will allow you to take it out.
10. Push out and remove the two pins from the receiver.

Remington 870 Disassembly and Reassembly

Remington 870 Disassembly and Reassembly

11. Take out the trigger group. If you have a pistol grip stock, you may experience a problem removing the trigger group from the receiver. There is no need to remove the stock; push the carrier forward to the magazine tube and then pull out the trigger group.

Remington 870 Disassembly and Reassembly

Remington 870 Disassembly and Reassembly

Reassembly

Reassembly is simple; it is the reverse process.
1. Insert the trigger group assembly into the receiver.
2. Align the trigger group with the holes in the receiver. Insert the pins and push them in.
3. Put the bolt assembly in; set it on top of the notches on the action bar assembly.
4. Slide the action bar assembly onto the magazine tube. Line it up with receiver.
5. Push the left cartridge stop, and slide the action bar assembly into the receiver.
6. Push the action bar lock upward, and pull the forend back to open the action.
7. Slide the forend forward approximately halfway.
8. Put the barrel on.
9. Put the follower and spring into the magazine tube.
10. This step is for the Remington 870 that doesn’t have the magazine extension, with the spring kept in place by the magazine spring retainer.
Install the magazine spring retainer. Insert a flat head screwdriver into the slot in the magazine spring retainer. Push the magazine spring retainer into the magazine tube and rotate it.

Remington 870 Disassembly Instructions Video: