Blackhawk/Knoxx SpecOps Stock (Remington 870) – Install and Initial Impressions


BFE Labs accessory before, during, and after the fact, James Mac has recently been going down the road of developing a personal fighting shotgun based on the Remington 870. We will be sharing his ideas and experiences with this project as time goes on, though until recently he has (rightly) spent more time working with the base shotgun than he has modifying it. That changed a recently when we sat down to install the Blackhawk/Knoxx SpecOps Stock on the 870.

The Knoxx SpecOps Stock has been around for a few years now, only more recently becoming a member of the Blackhawk Products Group family. The SpecOps Stock combines the Knoxx recoil dampening system, with an M4-style four-point adjustable stock and pistol grip. The implied advantages are that of adjustable length of pull (from shorter than factory stocks, to longer), the control of a pistol grip and improved recoil management. For a home defense/tactical shotgun these features not only make sense, but are fairly closely related at a few points. A shorter length of pull makes the shotgun both shorter overall, as well as more controllable. The additional recoil dampening features of the Knoxx design, and the greater controllability of the pistol grip, serve to enhance this at least in theory.

The SpecOps Stock is available as a complete kit with a replacement fore-end (which is what was purchased). The replacement fore-end is somewhat longer, and more robust, than the factory piece. This increased length and robustness provides a superior grip for a variety of arm lengths and hand sizes than did the factory piece.

Installing the stock itself was fairly easy. To remove the factory stock the butt-pad was taken off, allowing access to the stock-screw which, upon removal, allowed the stock to separate from the receiver. Once the factory stock was removed, the Knoxx stock was prepared for installation by removing the rear M4-style buttstock (pulling down on the adjustment lever, to release the catch, and sliding it off the assembly), then put in place and screwed down with the Allen-key (hex wrench) provided. Once the body of the stock was in place, the adjustable buttstock was replaced onto the assembly and installation was complete. As expected, this was an easy process. The manual included with the SpecOps Stock provided very complete, well detailed, instructions on this process.

Next came installing the fore-end. Ostensibly, this would be as simple a process as installing the stock, despite the fact that the included manual contained a dearth of instructions. In reality, most of the entire process was simple, save the part where the fore-end didn’t fit the slide-handle.
To remove the 870 fore-end, the barrel retention nut must first be removed, allowing the barrel to be separated from the weapon. Once the barrel and retention nut are removed (this will necessitate removal of the extended tube, if you have one), the fore-end retention nut must be removed. This is what holds the fore-end to the slide-handle, and it requires a spanner of some sort. Once you remove the fore-end and slide-handle assembly from the feed tube, a flat bar the thickness of the spanner-notches and width of the nut is the necessary tool to remove it. Not having a tool handy to do it, James and I let this be an excuse to go down to Calibers where a nice fellow by the name of Tony got the nut removed, and set about installing the new fore-end.


Left to Right: Remove the Extended Tube; Separate the Barrel from the Receiver and Tube; Disengage the Pump from the Bolt and Slide Off; Use Needle Nose Pliers as Spanner (or Proper Tool) to Remove Retention Nut; Separate Original Fore-End from the Slide-Handle.

Or it should be said, trying to install the new fore-end, anyway. The Blackhawk/Knoxx fore-end didn’t fit. It would not seat on the slide -handle completely, due to poor tolerances in one area which created almost an inch of stand-off from the seated position.

The red arrow illustrates where the pump assembly jammed on the new fore-end. The blue arrow indicates where the assembly was supposed to stop.

Tony agreed with us that grinding down the interfering plastic would be a workable solution. He also suggested that a pair of needle nose pliers would work to put the fore-end retention nut back on.
Armed with that advice, we went back and did the only logical thing there is to do when parts don’t fit: Broke out the Dremel tool. While Dremel gunsmithing is frowned upon (or should be at least), in this case the problem areas were very easy to identify, and mark for reduction. A few minutes of careful grinding later, and James had achieved the fit he needed.
Once the fore-end fit onto the slide-handle, everything went back together fairly smoothly save a few instances of not being smarter than the shotgun. (Having a set of take-down instructions for the 870 might prove handy to you when doing this, say the two guys who went on memory and struggle.) Essentially everything goes back on in reverse of how it came off, and you’re done.


Left to Right: The Areas to Relieve Marked w/ Layout Dye; Performing the Relief Grinding; The Fit post-Grinding.

Realistically, performing the necessary relief grinding to adjust the fore-end was not a difficult or particularly arduous task. No great amount of material had to be removed, and after it was removed the fore-end otherwise fit perfectly. The issue taken is that, great or small, such grinding had to be done at all. In a market dominated with near-precision components made from molded plastics and polymers, there is no excuse for an industry leader like Blackhawk to deliver products with such poor tolerances. Certainly not when it happens repeatedly (Several examples come up in a very brief Google search. I’m sure others could be found with more than fifteen minutes effort. The first two I found, http://www.calguns.net/calgunforum/showthread.php?t=235388 & http://www.zombiehunters.org/forum/viewtopic.php?f=16&t=58513 – Both pertain to the Mossberg 500 units, but occurrence is occurrence. Note in the ZH thread that one gentleman notes that a Blackhawk rep encouraged simply modifying the fore-end to fit).
Of course, Blackhawk never once in their literature says that the fore-end fits. The packaging says “Stock fits” and not more. The installation manual has a handy bit of fine print at the end that says that they make no guarantee that any of it will actually fit the specified model of shotgun. The overriding statement from all of this seems to be; Be prepared to fit this component. Something we’re a bit used to from wooden furniture, but might come as a surprise with polymer.

With the stock and fore-end installed, the 870 feels far better than it did with the factory furniture. The shortened length of pull provided by the collapsed stock, in addition to the more robust fore-end allowing a fuller grip, provides a much solider feel to the manipulation of the weapon.

Initial Impressions:
A few days after installing, we took the SpecOps Stock outfitted 870 to the range for a brief session. We began by shooting from standing positions to function check the firearm and stock, and then moved on to actually running drills for the rest of the day.
As predicted, the shorter length of pull, pistol grip and recoil compensation of the SpecOps Stock provided greater control and faster follow-through than the factory furniture. This benefit carried over to shooting from unconventional positions as necessitated by some of the barricades we’d erected.
Despite the fitting that had been required, the fore-end proved to be aproblematic for the entire afternoon of shooting. The fit, other than in that one area that necessitated relief, is fine and in no way inhibits the function of the firearm.
Two issues were noted with the stock: First, the stock necessitates a cheek-weld somewhat different than many may be used to. At the forward part of the stock-tube there is a swell, which can contact the shooters cheek-bone when a head-forward cheek-weld is used. The problem is that this point of contact will take recoil energy before the shoulder, thereby battering the shooters face rather hard. To counter this, shooting with the head raised somewhat (even more than one may be used to for shooting the ‘gauge) is necessary. While this didn’t compromise sight-picture or other factors for either James or I, it did take some getting used to. Blackhawk does offer a bolt-on cheek-weld riser to allow users who prefer a more aggressive weld to maintain their structure without punishing their face.
The second issue encountered was that, after a couple hundred rounds, the stock screw had loosened itself significantly. No thread locker is included with the stock package, nor does the installation manual suggest its use. Now, this is more of a “shame on us” issue, as the application of thread locker should have been an obvious step, even without guidance, and we overlooked it. We mention it here as a note for others.

After that range session and having it awhile James says he is pleased with the SpecOps Stock thus far, and that it is meeting his needs quite well. We’re both looking forward to spending even more time working it out on the range, along with other upgrades to the 870 as time goes on. A more detailed evaluation of the SpecOps Stock is forthcoming, once we’ve spent more time with it on the range, and with other shooters getting to try it out. Stay tuned!

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4 responses to “Blackhawk/Knoxx SpecOps Stock (Remington 870) – Install and Initial Impressions”

  1. AltheDago says:

    I ran into a similar problem with a run of Surefire forearm lights I was installing on agency shotguns in Seattle about 13 years ago. All of them required grinding out the forearm in order to line up the forearm retention nut withe the slide.

    • BFE Labs says:

      Al – Thanks for sharing that. I’m beginning to think that best-practice with installing polymer furniture is to be ready to make some adjustments to it.

  2. S. Dee says:

    I just installed a Blackhawk/knoxx Specops stock on my Remington 870 tactical 12ga. It was installed per instructions per blackhawk tech service. I had read about removing material with a dremel tool and I was not in favor of doing that. Blackhawk tech service told me to remove the orginal forend (I did purchase a good tool to remover the forend slotted nut. I removed it and slipped the replacement forend on and with 3 taps with a block of wood and a hammer (per blackhawk techs) I had the forend in the correct position and replaced the slotted nut. I replaced the barrel and all worked fine. Another note: you do not have to remove the magazine spring for this installation. One individual on the internet actually showed removing the magazine spring. So with this, I would recommend that anyone with questions, make a call or email Blackhawk tech service.

    • BFE Labs says:

      Per this thread, http://glocktalk.com/forums/showthread.php?t=1374480 , on GlockTalk, BlackHawk tech service may not be the best solution either.
      This is what the gentleman in that thread was told:
      “Thank you for your correspondence in regards to the issue with the forend for your Knoxx SpecOps Adjustable shotgun stock. The forend slides in to the slide tube, but stops at the beginning of the action bars; because they run into tabs on both sides. The front of the forend needs to be (tapped or pushed) hard enough; so the action bars cut through the tabs; and seats into place. If you have a rubber mallet, proceed to Tap (not to hard) the front of the forend. If you do not have a rubber mallet; then a block of wood and a hammer will do. The block of wood is to protect the forend. It should take only one or two hits to seat the forend. The tabs were put there to help give the forend a firm side to side feel.”

      Their advice to use a hammer to force the fore-end into place can result in damage to the weapon. In the case of this unit, had we tried to hammer it in and force the action bars to “cut in” as Blackhawk techs advised, we would not have had success. The amount of material necessary to be removed in this case was such that the action bar would not have been able to cut through it, and would most likely have bent under hammer blows.
      The thing about the tabs being put in to give the fore-end a firm side to side feel reeks of bullshit. I am unaware of any other synthetic fore-end with such “features”. BlackHawk has been guilty of sloppy manufacturing processes with many items, this seems to be yet another one, and rather than owning up they are making excuses.
      “Well, of course it doesnt work! Limited functionality is an intentional feature!”
      Piffle and Fah to PolloNegro.

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