The Remington Model 870 pump-action shotgun is one of the most popular guns for accessorizing. It has long enjoyed a reputation for rugged dependability and blue-collar affordability. So turning the 870 into a “tactical” shotgun for home defense and fast-paced target shooting is a rewarding home gunsmithing project.    
   Actually, it’s several small projects as the options are numerous.
   One of the most popular modifications is to add an extended magazine for more ammunition capacity. Choate Machine & Tool Co. makes a lot of 870 accessories, including a variety of magazine extensions that are easy to install.
   Remove the magazine cap and the magazine spring retainer, and then remove the magazine spring and follower as well as the barrel. Newer Model 870s will have two opposing detents or “dents” in the magazine tube designed to keep the magazine spring retainer in place, and these must be removed. The directions said to use a 3/16 "-drill, but that didn’t clean them up well enough, so I moved up to a 7/32 "-bit.    There will be burrs and perhaps some of the detent left inside. Use a half-round file—or better yet—a Dremel hand grinder with a rounded stone to clean them up until the magazine follower passes through easily. Polish out the grinding marks with a Cratex bullet-point tip in the Dremel tool. Fit the magazine spring over the stem of the magazine follower and install it in the tube, making sure it can easily slide the entire length of the magazine. Replace the barrel. Compress the spring with your fingers as you work it down into the magazine tube until you can slip the magazine extension over the spring and fit it to the top of the magazine. Carefully screw it down tight. Fit the support bracket to clamp the front of the magazine to the barrel and you now have a high-capacity 870 shotgun.

   Most tactical guns employ shorter barrels. I switched the 28" barrel on my gun for a 20" tube with sights. Then I upgraded the sights. I removed the factory sights and fitted the gun with XS Sight Systems’ 24/7 Standard Dot Express Set. The front sight is a large white bead with a tritium glow-in-the-dark center. Installing it was simple. With the supplied plastic punch and a small hammer, drive the old sight out of the dovetail, left to right—it’s easier if you clamp the barrel in a soft-jaw vise—then, reverse the direction to install the new sight. Mine was a very tight fit, so I made two soft passes with a parallel side, dovetail safe-file to open the sight ramp’s dovetail slightly before installing the new front sight.
   If your 870 has fiber-optic sights, it is necessary to replace the sight base. Loosen the clamping screw on the rear sight and slide it off the dovetail. Install the new base by reversing the process, and then install the XS blade with the single screw. The rear sight has a shallow V with a center, white, glow-in-the-dark line to lead your eye to the bead. Remember to tighten the locking screw securely. I did not, and my sight came off while shooting and fell into high grass where I could not find it.
   Another alternative is to add an optical sight. I used a Remington saddle-style scope mount. This is easy to install. Simply knock out the trigger retaining pins from the receiver, then slide the mount over the receiver until the holes line up. Now install the two supplied screws through the receiver and tighten them into the threaded side of the mount. Any optical sight can now be fitted using Weaver-style rings. I installed the new Aimpoint Micro T-1 PO49 sight. This compact red-dot sight is light, small and very fast to use.

   Almost every 870 makeover will include changing the stock and fore-end. The options here are almost limitless, and I can only comment on those I have experience with personally. I have used both the Choate Mark 5 Stock and the Knoxx recoil-reducing adjustable stock. Both of these pistol grip stocks are great. The Choate is a bit more comfortable at the range, but I also like the adjustable length of the Knoxx and the spring-loaded recoil reduction. These are simple bolt-on changes. Remove the old recoil pad with a Phillips screwdriver and reach inside with a flat screwdriver to remove the stock screw. Place the new stock on the receiver and tighten the supplied screw. The screw in the Knoxx stock is easier to work if you use the long hex screwdriver available from Knoxx.
   Fore-end removal begins with taking off the magazine cap or extension and barrel. Then, using a special spanner wrench (supplied with most replacements), remove the fore-end retaining nut. Slide the fore-end off and install the new one in the reverse order.
   Again, the possibilities are almost limitless. Choate offers a fore-end with a Picatinny rail to mount accessories. This rail can mount on either side or on the bottom. SureFire has an excellent fore-end with a built in high-intensity flashlight. There is an on-off switch on the left side and a bar on the right that turns the light on when it is squeezed and off when it is released. This is a great accessory for a home-defense shotgun.
   I added a Scattergun Technologies oversize safety. Remove the trigger group by pushing out the two pins in the receiver and then working the trigger free. Above the safety is a drilled hole with a pin through the top. Carefully push out the pin and catch the spring and ball. Slide the safety out of the trigger guard and replace it with the new safety. Replace the ball and spring. Push the spring down with a small screwdriver until you can re-insert the retaining pin. Install the trigger group back into the receiver.
   Wolff offers replacement hammer and firing pin return springs that will ensure more positive functioning. However, I don’t have enough room to cover their installation in this article.
   My 870 is no longer a boring pump shotgun sitting unused in the gun vault, rather it is now my “go to” long gun for home defense.