I love rebuilding old Remington 870 shotguns. The rattier the donor gun, the more I enjoy it. In this article the donor gun is an old 20-gauge Remington 870 Express that was used as a hunting gun for a number of years. We decided to give it a facelift and re-purpose it as a home defense shotgun. 20-gauge shotguns are an excellent choice; the more compact design, coupled with lighter recoil, makes it ideal for newer and smaller framed shooters.
I ordered the following supplies from Brownells:
Here is the donor gun. An 870 Remington Express 20-gauge shotgun coated in a homemade rattle can camouflage.
Before working on the gun, I make sure the gun is pointed in a safe direction, is on “safe”, and the chamber and magazine tube are empty.
To strip the gun, I begin by unscrewing the magazine cap.
The barrel can now be removed.
Depressing the left side shell latch, allows the forend and bolt to be removed.
The forend and bolt are removed.
Using a trigger plate pin tool, the front and rear trigger plate pins are removed.
The trigger plate can be removed from the receiver.
This special Magna-tip bit allows removal of the recoil pad screws without damaging the pad.
A large, flat-blade screw driver is used to remove the stock bolt.
To remove the forend from the forend tube assembly, the forend tube nut needs to be removed. Since I don’t have the 20 gauge tool (the 12 gauge is too big) I used a set of pliers as a spanner.
This picture shows how the pliers engage the forend tube nut to remove it.
A magazine retainer tool is used to remove the magazine retainer. The magazine spring and follower slide out once it is removed.
The disassembled 20-Gauge Remington 870 Express.
The receiver is secured in a milling machine vise. The centerline and front edge are located. This can be done using a drill press or hand drill if you don’t have access to a mill.
A centerdrill is used to spot the location of the front hole. The front hole is 5.885″ from the front edge of the receiver and the rear hole is 7.335″.
A #33 drill is used to drill a clearance hole for the tap.
Finally a tap guide is secured in the milling machines chuck and a 6-40 high-speed steel tap is used to form the threads.
The process is repeated for the rear hole, which is only .375″ deep. The metalwork on the receiver is complete.
The bead on the bead base of the barrel needs to be removed. On most 870s this is pinned and soldered in place and you can’t unscrew it. A file makes short work of removing it.
With the bead removed, the front sight fits in place on the bead base.
The stock on this gun is on the long side, especially for a defensive gun. I decided to cut off an inch.
I use a scribe to mark the new length all the way around the stock.
The stock is then aligned in the miter saw. Mine is equipped with a laser, which makes following the scribed line easy. Shims are placed underneath the stock to make sure the cut is square. Note the square on the right side, this ensures my pad won’t be canted.
A Limbsaver recoil pad will be installed. The manufacturer provides a template to aid in installation. I tape it to the rear of the stock.
I use a center punch to mark both screw holes.
A 1/8″ drill bit is used to drill two pilot holes 3/4″ deep. The tape tells me when the holes are deep enough.
The screws are inserted into the recoil pad and coated in wax. The recoil pad screws are tightened.
I use a scribe to carefully trace the profile of the stock onto the recoil pad.
I use a file to spread a light coat of chalk over the recoil pad.
I rub the chalk into the recoil pad. The scribed line is now highlighted.
I’m using a B&R recoil pad fitting fixture to shape the recoil pad. I adjust the bottom of the fixture to match the shape of the stock. The recoil pad is attached to the fixture with machine screws.
Here is the B&R recoil pad fitting fixture installed on my 12″ disk sander. A belt grinder would work as well.
I start with an 80 grit disk and grind away the bulk of the excess recoil pad.
I follow up with a 120 grit disk. The recoil pad has a fine finish on it.
I rounded off the top edge of the recoil pad. This allows the shotgun to be quickly shouldered without snagging on clothing. Note how well the lines of the recoil pad match the stock.
This gun has a longer, sporting type forend (top). Note how much longer it is when compared to a OEM 870 Police forend (bottom). The longer length can interfere with a side saddle and blocks the shell lifter when retracted into its rear most position.
The miter saw makes quick work of shortening the forend. I hit it with a disk sander to break off the sharp rear edge left by the saw blade.
To remove the layers of old wood finish and spray paint I use a cabinet scraper.
With the paint removed, I gently sand the stock with 120 grit paper. Since I will be staining this stock, I do not sand it any finer ( I used to build a lot of furniture, and this was a guideline we used.)
A quick pass with a dark walnut colored wiping stain and the stock looks better then new.
Unfortunately, I lost my pictures of the metal refinishing process. I degreased all metal parts, blasted then at 80 PSI with aluminum oxide and coated then in Graphite black Cerakote. Once the parts were cured in the oven, I epoxied the front sight in place over the bead base and I reassembled the shotgun.
The smaller frame of this 20-gauge gun make for a light, fast handling package.
Right side of our rebuilt 20-gauge Remington 870.
A side saddle allows the gun to carry additional ammunition.