M*CARBO Brotherhood

AR-15 Buttstock Adapter For Your SUB-2000?

I got a little bored and wanted to try to get better a 3D modeling. So here is this…

It’s a one-piece buffer tube for our Subs. It pins in the same and replaces the existing buffer.
You would have to machine a pin that sets flush in the tube, the stock will stop it from sliding out.
Also, the front sights won’t allow it to fold. It could be made longer and notched for the sight.
But the stock would have to be notched as well.

If anyone with a printer wants to try it, let me know.

EDIT: I’ll just share the file here on Thingiverse

EDIT AGAIN: The file won’t be available for 24 hours, new user thing, I guess.


This is just meant to be a template to later be machined out of aluminium.
Please consider that 3D printed PLA may not be suitable for this application.
It may work, it may even work well, but I can’t recommend using it. Just saying.

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This picture is what renders on Thingiverse, suppose that is what it will look like.

I printed about 1/2" or so to see if it fit the tube on my Sub and also a spare buttstock.
It was very snug on the tube and loose on the stock, so I made a few adjustments.

I don’t have the skill to make a decent print of this, but I was able to order it for $24.44.
Thingiverse has a “Order Print” button right on the page.

After I receive it and try it out, I can move on to the next step.


@ValorSolo don’t suppose you can design a one piece full length handguard for the S2K can you? That would be amazing! :grin::+1:


I will look into it. I love this CAD stuff.


Saw this over on the ktog, some dude apparently designed and made his own stock for the sub 2000, and it actually looks really solid: https://www.thektog.org/threads/introducing-the-first-upgraded-stock-designed-for-the-sub-2000.271646/

Its got adjustable length of pull and looks like it is more comfortable than the factory stock, and imo looks kinda better than the factory stock in general design wise.

Idk if this guy did it as a one-off or what but maybe MCARBO should think about working with him to mass produce it! I bought a MCARBO buttstock pad for mine but jeez a fully upgraded stock with adjustable length of pull would be fantastic.


Also i had no idea this thread was already a thing, thanks mods for moving it to the right place! :smiley:


Yer good brother, we’ll get you squared away!

Now dude from ktog’s post, his design seems very rudimentary, bulky, square, and takes everything we hate about the factory buttstock and capitalizes on it only bigger. Nice try though.

I do like the lever activated LOP idea, but again I think anything aftermarket or custom should be both more elegant looking and ergonomically more functional. :+1:


The guy said he 3D printed the parts (that’s the rudimentary look). Actual manufacturing of the part could slick it up very nicely.


Interesting points, though honestly i think the fact that it capitalizes on the look of the factory buttstock is more of a benefit rather than a disadvantage. This is why i bought the mcarbo buttstock pad, because it reflects a lot of the same look of the factory buttstock… like ive seen the mods some people have done where theyve managed to put an ar15 stock on the s2k and it just looks very out of place.

Like for all its faults, the factory buttstock looks nice with the rifle, so if theres some sort of marriage to be had between making it look like the factory stock but making it much more functional, that’s the best of both worlds i think. and i think that guy really nailed it for the most part. especially wow after checking out the earlier thread, that thing has come a long way with the different designs.


About time someone put something like this together! that thing looks great, doesnt look like hes got them for sale but shoot i would pay upwards of $100 for an upgraded stock like that. The stock on the sub 2000 is definitely the part ive wanted to upgrade the most.


This is the absolute #1 thing I NEED (I already have all the other upgrades, and those are just wants :wink: ) - I’m just guessing here, but I would bet that this might not even be too long for me. I am 6’3" and have a unusually long LOP.

Back on topic though, and this is a fair departure from the general idea of the thread - but still on topic…rather than an adapter for collapsible AR style stocks, why not a stock specific for the s2k that takes advantage of the locking pin that the carbine already has? the same one that is used to adjust the current butt section. It seems to me that the current longest LOP is likely to short for even the shorter end of the LOP spectrum for average shooters - for a truly “good fit” LOP that is, not that we don’t all make it work.

If we, you rather, just built out a poly butt section that was longer in general, ie just “tube” where it contacted the actual bolt tube, and then some distance behind that was the actual stock, I think this is really what we all need. It also allows us to design around all the constraints. the top portion can be cut out to allow the locking mechanism to still function when folded, and to give clearance for the front site post when folded.

This sort of setup would also allow for many more positions than just three, in addition to longer overall LOPs. So, similar to the AR collapsible style, just not as quick to implement changes - though I would hazard a guess that most of us are not regularly meddling with our AR stocks either…


Going a step further it also allows us to address a lot of other concerns - like the pitch/comb/etc of the butt stock itself, as well as to introduce a lot of various “butt pads” to adjust the pitch, or plates/cheek rests to adjust comb to shooters preference/needs…even a cheek “well” to allow someone to get down low enough to consistently use the iron sights.

In short, although an adapter for AR style adjustable butt stocks seems like the “easy” solution at first - long term it looks like the “real” solution is a custom job made specifically for the s2k because it allows us to address the specific peculiarities of the platform and to think ahead in the design to address them. :ok_hand:


@Jester Welcome to the Brotherhood. Don’t forget to go to the First Post Here: Introduce Yourself! thread and say Hi to everybody.


Welcome to the Brotherhood, @Jester .


Great thread. Here’s what I’ve done with the Odin Works Zulu on my sub2000. I modified the kit supplied buffer tube. Fits on really tight, tons of adjustments, stock pin keeps it in place.

Bunch more pics and the build on the KTOG board…




I was considering something like the Sig Sauer MPX / MCX Collapsible Stock, parallel rods down both sides of the tube, riding a little high. top lock would not need redesign, front sight would fall between. Something close up in a post above (#121), but not quite, and the rods could be fully shrouded. I could have my engineer son draw up some CAD, but I have no facility to manufacture a prototype.


Even have it UNLOCK when extended…

I would buy it. IF you want a CAD mock up, let me know.


Welcome to the Brotherhood, @Sabre9mm.