Bird Gun to Zombie Killer: Upgrading the 870 Pump Shotgun

Many shooters love the Remington 870 pump shotgun in the field, and I have owned many 870s I used for doves, ducks, and bucks. The gun has a basic appeal as a game-getter.

Here’s the 870 in its original form. The author wanted an adjustable buttstock instead of the fixed stock shown, which lead to a sizable upgrade overall.

I have also owned one self-defense version, a Remington Model 870 Express Magnum Synthetic 12 gauge, which I bought for $325 six years ago. The 870EMS is a capable home-defense scattergun by any measure. Mine had a matte-black synthetic-stock, a 3-inch chamber, and 18-inch barrel. It weighed 7 pounds unloaded. The fixed buttstock had a length of pull of 14 inches, a drop at comb of 1.5 inches, and a drop at heel of 2.5 inches, with no cast.

But since I’ve become an AR owner, I love the flexibility of a six-position collapsible stock, so I began looking around for 870 replacement buttstocks. Grazing online at, I found several choices and settled on a Blackhawk! Knoxx SpecOps Recoil Reducing Shotgun Stock for Remington 870 (CTD Stock No. 2-BHK04100-C, $81.19).

Installing the new Knoxx buttstock was easy. Using a ratchet-handle driver with replaceable tips, I removed the Phillips-head screws holding on the existing buttpad, and then switched bits and took out the buttstock screw. I pulled the solid buttstock off. Then, using the supplied long Allen wrench, I screwed the adjustable Knoxx stock onto the gun in less than 3 minutes. Next, I installed the replacement forend supplied with this kit. Putting the forend on took about 10 minutes with an 870 action nut wrench.

At the Range Next, I tested the stock components for function. I had access to an identical 870 sans modifications, so I could compare the before-and-after guns shot to shot. Firing a range of shells from light 2.75-inch bird loads to 3-inch steel magnums, I immediately liked the Knoxx buttstock. It uses a spring-loaded recoil-absorption system to reduce felt recoil and muzzle rise. The soft, thick rubber recoil pad was 5/8 inch thick, and it noticeably cushioned the blows of the magnums. Of course, being able to adjust the LOP to exactly what I wanted made a big difference in fit. Also, the ergonomic plastic pistol grip with finger grooves improved control for fast follow-up shots. The ribbed replacement forend provided a good gripping surface, though the original forend was fine as well.

Fine Tuning I later added XS Ghost Ring sights and a Wilson mag extension to really get this 870 where I want it. The Wilson Combat machined-steel two-shot magazine extender (Wilson stock #SGET-RH-2) comes with a magazine spring and high-visibility chartreuse nylon follower. Installing the XS Ghost Ring sight required drilling and tapping my 870’s receiver, which I had done at a local gunsmith shop. Many shotguns are already drilled and tapped, and in that case, the X

Blackhawk Knoxx SpecOps Adjustable
The SpecOps stock uses a spring-loaded recoil-absorption system to reduce felt recoil and muzzle rise

S sights are drop-in installs. Of the components, the recoil-reducing stock offered the most noticeable improvement over the standard version.

On my gun, I probably didn’t need the Wilson mag extension, but if you’re upgrading a shorter 870 tube, that extension increases capacity and adds a front sling-attachment spot. The XS sights are another big upgrade over the basic 870. If you intend to shoot slugs and want to hit what you’re aiming at, I consider them to be vital additions.

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Comments (9)

  1. I also have a Remington 870 and installed the same stock. But for ghost ring sights I went with the LPA BAR series front and rear sight. I like that it has wings on the front and rear sight that helps to protect the actual front sight post and the rear sight aperture. Haven’t had a chance to really put it through its paces though. But so far it feels good and the sights are super easy to acquire. 🙂

  2. I too have a Rem 870 express synthetic similar to the author. However, instead of the Blackhawk upgrades, I installed the Phoenix Technologies tactical stock and Mako foregrip w/ rails (SHT-269 and 2-MAKPR870 respectively). One thing I like about the Phoenix stock is that it is comfortable and very easy to remove the stock and just leave the pistol grip making it a much more nimble shotgun for home defense purposes. The Mako foregrip has rails that I attached a powerful LED light to the side rail that has a pressure switch where my hand would be. The 870 is just an amazing shotgun because of its good design and near infinate upgradability.

  3. Great article and nice accurate feedback. Keep it simple. The Marines did with the 870 and others in Nam. Great point weapon. JohnSeaz has it right on and I am a bit jealous he has taken courses I would love to take from Frontsight. Maybe one day. I have the 870 Police magnum and an Sig AR15. Both have their place and one can argue for days which is better but I am comfortable with either. I haven’t changed my Police Mag and wouldn’t. I too have a wrist problem and would have to consider the rear stock change for that. The 870 is the finest weapon ever made IMHO. I have hunted all my life and had a few other reasons to carry one out of country. I would never be without one. I did get rid of my hunting 870 express’s.

    Keep it simple, best advice given here. If it isn’t you better train hard to make it simple for you. It is all in the front sight so if you can’t see it fix it. Aiming is automatic for me and I can’t remember what I do and if I tried I would probably miss. You need a good sling or someone will jam that gun where you don’t want is. You will also need it if you have to go to your secondary weapon.

  4. I own the Knoxx stock with the recoil absorbtion but, I had to take it off the gun. I had installed it to help handle the 3″ Turkey loads but found that the spring would bottom out. When this happened it was like a smack in the face. When checking the pattern of the gun with several types of ammo it left a bruise at my cheek weld point. I liked everything else about it and may try to trade for one without the recoil absorbtion. Meanwhile I have the factory stock on the gun.

  5. If you need something done with a shotgun the Remington 870 is capable of doing it. I have 10 of them from 20 ga to 31/2″ 12 ga and they all work everytime.
    When I was a new cop about 40 yrs ago, I wanted my own shotgun for duty use and hunting. I bought a used Remington 870 with 20″ barrel and the old style rifle sights. Its only a 2 3/4″ chamber gun, but haven’t needed 3″ for “social” purposes.I was dept firearms instructor for 27 yrs and academy firearms instructor for 6 yrs and used that same gun, all that time. It has thousands of rounds thru it and is just as reliable as ever.
    Only bad thing about the remingtons is if you leave them unattended in your safe they breed and you will wind up needing a new bigger safe. I’m big fan of remington rifles too. Love the 700’s, mdl 7(my favorites) and the 7600’s
    My current “social” gun is an 870 police magnum with knoxx stock, drilled and tapped for receiver sights, has an Eotec sight, side saddle shell holder and magazine extension, with a extended light, modified choke for use with OO buck. Don’t have to have all that stuff a plain vanilla 870 will work to protect your bacon too.

  6. I agree wholeheartedly with JonSeaz.
    I own 4 Remmys. An 1187 Sportsman with a Max4 Ramline stock for waterfowl hunting. An 1100 20 gauge that I set up for trap for my wife. Her original 870 Express 20 gauge, now wearing a laminate stock to replace the original gumwood. And finally an 870 Express combo 12 gauge. After serving as my waterfowl gun for many years it has changed roles to become my main HD gun. I also added the Knoxx Spec-Ops Recoil-Reducing stock but ditched their(in my opinion) cheesy forearm in favor of a SureFire unit with the built in tactical flashlight(which cost almost what the gun itself initially set me back!)Since the gun came with 2 barrels; utilizing the 20″ RSS barrel was a no-brainer especially since a plain, beaded 18.5″ was more money that I could justify to myself for the 1.5″ shorter barrel! I added a Wilson Combat/Scattergun Technologies 2 round mag extension that I picked up for $15 at a gun club flea market and secured it with a CDM Products basic barrel clamp. If you have yet to check out the clamps Scott makes; do so soon! He makes great stuff and it is highly affordable. At the same time I added a CDM machined aluminum follower which required the dimples inside my mag tube being ground down with a flexible shaft rotary tool and some quick re-bluing. Last item I intend to add is a Mesa Tactical 6 round side saddle so I have shells close at hand if need-be since I refuse to leave a loaded gun around where one of my two labs could knock it over. That may sound rediculously paranoid; but that’s me. I have given thought to adding a sling and may yet as it will merely require adding a front sling attachment to the CDM barrel clamp.
    Next up is finding an older, used 870 (hopefully with an 18.5″ barrel) to install the synthetic bird’s head grip I picked up at the same flea market onto for a nice, short package that can be left next to our front door in the umbrella stand.

  7. Amongst several shotguns, I own three Remingtons, an 11-87 Police, a Marine magnum, and an older 870 Express converted to a home defense weapon. I have attended the Front Sight Nevada 2 day tactical shotgun course, the 4 day course, and the 2 day skill builder. During those sessions I observed several students perform with a variety of shotguns configured in a variety of ways. Personally, I subscribe to the Clint Smith dictum of”keep the gun simple.” That has worked well for me. I also subscribe to the advice of J.D. McGuire of AI&P Tactical, builders of 870 police and home defense duty shotguns. J.D. preaches simplicity and advises that the 870 Express for home defense needs only a bead sight and only having the carrier dog follower spring changed to the heavier one used in the 1100 and the MIM extractor changed to the forged and machined one. I do like a Remington magazine extension and a Speedfeed IV-s Shortened Tactical Stock Set, but that is a personal preference and other mag extensions and stock work fine based upon my observations of many people in training. Being a short guy with shorter arms I like the 13″ length of pull and having a bum right wrist need the pistol grip. I like the Remington magazine extension because I like the forward clamp to support the extension and protect it from impact damage. Like Clint Smith, due to my old eyes, I install an XS Big Dot over my front bead. I also dehorn the gun, check it for function, and apply a bake-on finish. The Express 870 thusly configured really works well for me, is accurate with bird, buck up to about 35 yards, and slugs out to around 100 yards, and is very reliable and durable. I fire the more than 500 rounds required in the Front Sight courses without cleaning or lubing the shotgun. As for lube, I start the course with a wet gun, and use a high-temp moly wheel bearing grease on all sliding points, so the gun remains well lubed through lots of rounds. I like my short-barreled Mossy, Ithaca Deerslayer, and 11-87 Police, but when a shotgun really is needed depend upon my 870s.

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