M*CARBO Brotherhood

Full Length Forend


When I do the stock, I want to use the minimalist stock. I like them on my AR rifles and I have a spare. Would cut as shown in picture to reduce size and still maintain functionality.



@BReno have a look here @Dred did some really good work using the same idea.
AR-15 Buttstock Adapter For Your SUB-2000?


@Johnksg Challenge Accepted

Well John, I hope this is close to what you were thinking. Your post mentioned both FDE and Tan, but the colors looked almost identical on my monitor so I went with only FDE and then black/gray for contrast. The rear sight is gone as requested and the muzzle brake has been added. I kept the latter black/dark for contrast with the FDE. I did not find a good image at the correct angle of the specific butt stock you referenced, but mocked up two different though similar stocks. Overlaying color transparently so as to retain the underlying details is tricky, so the color is far from consistent or uniform, but it is close enough to give the general idea. (I basically start with a black and white or sepia toned photo that has the detail I want then lay the color on transparently; much like photographers once added color to black and white photographs – I’m sure graphics artists know more sophisticated techniques but that is the way I have worked out how to do it). I did one version of each stock with the short picatinny reinforcement and one with a longer rail down the whole side. The longer rail is probably a bit oversized and not 100% true to scale since it needed to be large enough to cover the rail that was already there in the image. This obviously won’t make any magazine covers, but it is adequate to show how a gun would look in a particular color with particular features.


That’s baddass @JoeFridaySays! Nos. 3 and 4 for me. I would retrofit to this version over my KT 4 Rail forend👍


@JoeFridaySays oh my, Brian you just gave me the vision for my next build!!

Somehow just seeing it in a picture just pulls it all together in my mind. Thank you brother!:+1::+1:


Given some of the interest expressed in this forend modification, I looked at the cost of building it. Remember though that the gun will probably fold all the way but it will not latch with this modification. Here’s what I found IF you have to buy everything:

Kel Tec S2K-1504 Gen 2 Forend Assembly $60-85 plus S&H
[Price depends on color. Black is $60 while OD & FDE are $85.]

2 pk 13 Slot 360 Tactical M-Lok Picatinny Rails $13.99 plus free Shipping from Amazon
[The top rail of the S2K has 17 slots so 13 slots comes very close to comparable coverage down both sides. You obviously can buy far more expensive rails if you wish, but you probably will not be mounting sensitive optics and the like on the side rails of a non-rotating forend, especially where those rails are themselves dependent on an M-Lok connection.]

Performance Services Stabilizer $44.90 ($35.95 plus $8.95 S&H)
[I’m guessing on this, but think if it will fit that adding the extra stabilization is probably a good idea since you will likely be mounting a sight of some kind on top of this segment and want it as solidly locked to the barrel as possible.]

TOTAL $118.89 to $143.89

If you already have a Gen2 forend lying around from where you installed a replacement on another S2K, you can knock $60-85 off that estimate and do the conversion for around $60.

Having said all of the above, this does seems like a natural fit for MCarbo to make. Even with the addition of some kind of stabilization brackets, it looks like a fairly simple two piece part to make from either injection molded plastic or aluminum; and I see no real point in the latter unless production costs would be less for aluminum. Startup tooling and production costs should be low in either case, so sales would not have to be huge to justify making the item. It is a natural companion for the muzzle brake, especially if MCarbo also develops and sells its own picatinny mount folding front sight which would probably be a huge seller itself once it had a place to mount.

And one more thing. Just for @Boomchucker, here are his two preferred versions with the MBUS front sight he mentioned. I tried it in FDE and it sort of got lost so I went with black for the contrast. If I can find an appropriate image, I will mock it up with the new MCarbo optic mount over the weekend.


@JoeFridaySays just a thought…

Why not send this to Chris? I would think MCARBO could turn this into an upgrade kit and add it to their product line. With their video instructions and a “one stop shopping” convenience it is sure to be a winner!


Run a mock up of the bottom one with rails all the way to the hinge.
That is whet I would like to have.
But then I am also looking for a young rich cute girl that wants to love a kept man.


@Turmeric1 I already had a similar thought since I did not like the look of that last opening showing so I extended the rail to cover it but did not go all the way to the hinge. I just hope it is possible to find an M-Lok rail that long although you could always combine a couple of shorter ones. I also added an angled foregrip for the ape-armed among us. :grinning: That foregrip could be moved forward another inch to provide even more support for the added section.


I doubt this would be a big seller by itself. It could offer a big advantage, however, in providing a base for other killer products that MCarbo excels at doing better than others but does not yet offer because there is no place for them - like a picatinny mount front sight.


I d not like having that rear bottom open but no choice with KT420 to be able to get the bottom front extended far enough to be functional.

Do not know about MLOCK but I do have ERGO rails that are 12".
I just need the time to mill them to bolt onto the KT420 sub frame.
Also I would like to have that frame be longer.

Ideally what I would want is the toprail end just forward of the OEM folded rear sight extending to the OEM folding lock position and the bottom rail going from hinge to just behind front sight mounting strap.

With it’s limitations I like the KT420 but would like to see someone design the same type of thing but for the S3K gen2. the kt420 was designed for the gen1 (with different muzzel side of the receiver) according to the CS@KT. I am waiting for the replacement KT420 fore end to arrive .


@Turmeric If you mix a cutoff Gen 2 forend with a KT forend that will give you Frankenstein 3? Or is it 4?
It will certainly cement your mad inventor credentials which were never really in doubt on this Forum anyway. :stuck_out_tongue_winking_eye:

I wish the top rail started just in front of the sight as well and do not understand why KT did not do that. I do not see any components that preclude sufficient thickness for the necessary molding unless the mounting bracket does. You were recently inside; what did you observe?


@Johnksg I hate to presume with a direct message to @ChrisNelson and suspect ideas that gather enough interest eventually come to his attention anyway.


I thank you for the support !
I guess I could sand the rail blocks off the top and bottom then I could run splices for 3 factory holes in the KT420ven That gives me 2 factory holes in the 420 on the top rail which has very little attachments that far forward… On the bottom i could run the do the splice in the back.
I have 2 spare KT rails I will use those for now as the donors of the splice.
When I have time I will mill the 12" for a full frame (hinge/front sight strap.
I would love to see a mock up as time allows.
Going to finish my wood floor.


I will see what I can do but I need a much better description. You see stuff in your head that unfortunately does not make it into the description - at least not in a way that I can understand. That may just reflect my lack of knowledge but I need a very detailed and simple description of what it should look like. If necessary, make a rough drawing, take a picture, add labels and upload that. It also would help if you can provide a sharp photo of the gun in the same orientation as those above showing the KT forend as well as a close up of the forend in the same orientation as I may not be able to find such photos online to work from. If you can take them against a white or light background it will make things a lot simpler for me. I know you can take such photos as I have seen them in your other posts.


My only complaint with the KT420 is the length. Wish it was longer. Looking at your renderings @JoeFridaySays (and thank you for the version showing MBUS!) brings it back to my mind. Be great if Kel Tec made a long and a short version. I’ve grown less enamored with my foregrip due to its position, even taking off the Olight to move it as far out as possible or off. Your design solves that with extra inches. Looks great, offers a substantive style change while adding functions.

I think this idea is well worth considering by the Powers that Be👍


@JoeFridaySays Thanks for the renderings , since I have no imagination, it helps me a lot to see what people are talking about.


@JoeFridaySays just imagine if MCARBO made a receiver rail that attached at the hinge pin! Now that with your concept would open up a whole world of possibilities!


I should be clear in stating that it is rare for any one of us to ever truly “design” anything on our own. We typically build on the ideas of others. As far as I know, it was @Flogrown who first had the crazy notion of using the cut off front of a Gen 1 forend as an extended handgrip in front of a KT forend.

I simply built on that idea to show @BReno a way he could use part of a Gen 2 forend with its top rail to do basically the same thing and thus be able to mount a flip up front sight at the very front of the firearm. The utility of that concept – especially with the Gen 2 rails – quickly became obvious to me and others and things grew from there.

Like a good Marine, @Johnksg wanted to see more and politely pushed for mockups “that more than a few members would find interesting.” I knew I really was designing his next build, :smiling_imp: but indulged the fiction since I wanted to see what it looked like as well.

And the interesting requests keep coming. I will do what I can, but I do have a real job, so no promises. You can help by providing info of the type I requested from @Turmeric1 in the post above.


@Johnksg It would indeed. But just opening up that real estate just in front of the rear sight would be awesome. I have been exploring ways to combine a 1-6x optic with the SeeAll sight and was looking at various options to make use of that space just in front of the rear sight, including reversing a cantilever mount. Any transition from the existing rail to that area that will still allow folding is going to be extremely tricky. A QD mount that will hold 5 inches of cantilevered weight may not exist; or if it does will cost a ton.