AR-15 Buttstock Adapter For Your SUB-2000?


Edit to add: I see pictures land where they want. My fault for continuing to build the post during uploads.

Awesome @casper3oaks … your build is what started me down this path to happiness.

I’m cramming to finish work today, but I’m going to drop pics for now.

Folded as much as she folds. Front sight tucked into buttstock cutout:

Opened up:

Under the buttstock:


@Dred OK I’m a believer. When do they go on sale :smiley: I have been following along with bemusement ,not sure if I wanted to jump on the bandwagon or leave well enough alone. Now I just hope that someone makes them , or at least gives detailed directions on how to replicate your work. Well done sir, well done indeed :+1:


Yup, that’s the prototype right there. Hook a brother up!!


Matt, not sure what is going on but could not log into the forum with my Mcarbo account. Figured your forums must have been separated from the Mcarbo sales site and the fact that it let me use the same user email without giving me an error saying “that user already exist”. Just logged out of the forum and back in with my normal account I’ve made purchases with (and just signed in on the sales site with) and it still doesn’t work, so…. Sorry If it’s a problem but it’s one I didn’t even know was a thing. Delete the new account I just used to make posts to if you need.




That looks Great Dred! Nice stock choice. Are you going to attach the latch to the top to hold it in place? If so when your mocking it up make sure you get it a little closer than you think ya need. Mine ended up working fine but wish I had it a little tighter. Just rounded the piece out with a dremel to fit your stock and use some gorrilla glue or 2 part epoxy. Mines had falls and it’s held up great.


K … so … let’s say you need one of these tomorrow - that is: you can’t wait for @ChrisNelson to offer a professional grade example if he’s gonna hook us up. Note: I’ll buy one just to hide all the sins staring y’all in the face here.

We are looking at a slightly modified AR 15 carbine length buffer tube - $10 to $20.


For starters, I had to cut it to the length I wanted. If you look at the bottom of the tube, you will find a track that allows 6 LOP settings. In my case, I cut the tube exactly where the track began. If you are familiar with the M*Carbo bolt tube cover - I retained the full length on the cover and the remainder of the AR tube is butted right up to the bolt tube cover.

Interference fit:

Ok, the Mil spec AR buffer tube does not just “slip” over the Sub 2000 bolt tube. I chose to use a brake cylinder hone (auto parts store/Snap-on Truck or Amazon - get one with 1" in the operating range) to grow the inside diameter of the buffer tube until it just slides over the bolt tube. I was careful to stop before I created a sloppy (ultimately noisy) fit. Honestly, it didn’t take much care 'cause I went through a fully charged 4 hour capacity Lithium Ion battery on my hand drill - that’s a couple hours of “honing.”


We know that we access the bolt through the bolt tube. So, we need to create a means of installing the bolt stop with the cover in place. This was pretty easy even if my metal work suggests differently. I will leave you to your devices on how to create this access. I used a combination of cutoff wheels, grinder and files.

Bolt stop pin:

This will require the greatest degree of precision. You need a hole put clear through both sides of the AR buffer tube which lines up perfectly with the holes in the bolt tube. Admitedly, I struggled with this - largely, because I refused to measure or mark anything. I started with a small hole which successfully hit one side of the bolt pin hole then I carefully grew the hole until I had a match on one side. Then … I crossed my fingers and drove the hand drill right through the second side of the buffer tube. Full disclosure: I was less than perfect and I will be watching my stop pin carefully.

Sling Mount:

Yes, the Minimalist stock has a QD sling mount directly ahead of the adjustment lever.


I cut the lock point off the top of the factory bolt stop so that it can be fit into place through the access cutout. I used a 3/8" clevis pin in place of the factory bolt stop pin so that I didn’t have to shave down my factory pin in case I wanted to return it to factory configuration.

I’m done. But, I could go about making a cutout on the bottom side of the buffer tube to allow the front sight to slip through. If you look at my previous post with pictures, you’ll see that it does not fold completely. The front sight is preventing a complete fold where it is impeded by the bottom of the buffer tube. Since I’m not certain I’m keeping the front sight … I’m not clearancing further. But, for those that do, or those that will … I still have the latch portion of the bolt stop. I could attach this to the top of the Minimalist and use the adjustment lever to “lock” it closed. I’m not doing this 'cause it would cost me about an additional second to deploy it and it’s a defensive tool. If I discover that I’m banging it up due to lack of latch - of course, I will revisit.

I estimate my length of pull to be the equivalent of the factory stock fully extended plus the ATI recoil pad. This is just what works for me, and there are shorter and longer settings available for other shooters. It must be returned to this length configuration to tuck the rear sight through its hole in the buttstock - this way it is ready when I unfold it.

I have not put a ruler to anything. If you want measurements, describe what you want and I will measure for you. I can tell you that I would have to clearance for the charging handle to run this stock at the shortest length of pull I can select. I fired it at the shortest setting without problem, but I wasn’t going to be able to lock the bolt back. The charging handle did hit the buttstock but nothing cracked or fell apart, so …

Finally, if I had to start anew, I would start with a Commercial spec buffer tube and stock. The commercial spec has a slightly larger inside diameter and the “honing” should go faster as there is less material to remove.

Full Length Forend

Excellent write up! Sorry I forgot to mention I used a fold-able front sight which is the only reason I’m able to fully close mine. Another possible project for @ChrisNelson


Best part about reading this @Dred is I can wait for the @ChrisNelson hookup cos I’m definitely not goin’ through all that. But WoW!! That’s the coolest mock-up of a possible alternative buttstock on a Sub2000 I’ve seen anywhere. Your use of the minimalist in your design is in keeping with the original Kel Tec buttstock but with more style and better function. Love it!

This could be the base model from which MCARBO starts something. I’d buy it. :money_mouth_face:


@ChrisNelson, please look in to this, I think I might take a stab at it my self since it’s not really an expensive project but if mcarbo made one, I’d just buy it…


@JoeFridaySays this concept is F’ing brilliant.


Quickly whipped up a pic I drew on my phone. Don’t know if it would work?

Basically in concept it would fit just like stock, the U shaped thing would be your adjustments, like the magpul stock squeeze up and adjust. The U locks on the stock cross pin thus locking it in place. Top would be slotted to clear the locking mechanism. Cross pin hole would be slotted to allow movement. Butt pad could be standard rem 700 bolt pattern or magpul pattern?

Not that out would matter for me, since featureless can’t have a adjustable stock…

Another pic.


Sure would like to meet you out at the Juliff range someday to check out your buttstock upgrade. Give me a few days warning and I should be able to adjust my schedule to meet yours. Think what you have done is about the best alternative setup I’ve seen.


No prob and anytime. Running to Austin next weekend to pick up my newest 1911. Today, Tuesday or Thursday will find me with availability for a quick shoot. I’ll toss the Sub back in the truck; I read here between jobs and I’m near Juliff on those days.


If you are still available to meet out at Juliff tomorrow, Tuesday, I am also available. Just give me a time that’s good for you and I’ll meet you at the 25/50 yard range. Really interested in seeing the stock modifications you’ve made on your S2K.



Yes. I’m targeting 3pm @ the 25. I’m sending you my cell via private message. Presently, I think all I’ve got for 9mm is WWB 124g NATO. This is the stuff that used to bruise my shoulder with the factory stock. I’m not picky about what she shoots - just letting you know what I’ve got. I’ll also be running a mag of Speer Gold Dot 147s since this is the current business carry.



Great to meet you. I look forward to a round 2.


Thanks for meeting at the range today. Enjoyed shooting with you and picking your brain about the buttstock modifications you’ve made. The pictures you posted here were impressive, but actually getting to look at it and fire your S2K and be able to adjust to a length that was good for me really sold me on your idea. My S2K will have a similar modification soon. Also liked the sight you had on yours. Since you have that sight, why did you choose to cut the access hole in the top of your new stock? Why not just remove the front sight so it would still fold completely? What i my try first is removing the Kel-Tec front site and put a folding Troy Battle front sight on since i have a couple of them in my parts box. My idea is to drill a 3/8" hole in the back of the AR buffer tube. Then I could remove the stock, run a dowel rod into the buffer tube and release the pressure on the bolt stop and pin to remove the buffer tube, bolt stop, pin, and bolt for cleaning.
Thanks again for taking time out of your day and meeting me out there. Once I get mine modified we can meet out there again and I’ll show you what I ended up doing on my stock.


Can you tell me what folding front sight you are using? Are you also using an Mcarbo rear sight? I plan on doing the same modification to my stock that Dred did to his but want to try to avoid cutting a hole into the top of the stock for the front sight to fit into when the firearm is folded.


Stock access hole: I cut the access into the buffer tube to allow installation/removal of the plastic bolt stop piece (the Kel Tec piece with the evil latch shaved away). When I did a test fold, I saw that enlarging it a touch allowed the sight to tuck and give me a nearly completely folded Sub before the sight bottomed on the underside of the tube. I considered slotting the underside of the tube but decided it was close enough. Then I fit the stock to the tube and found my desired LOP. It’s not at it’s fully collapsed location so I did a little head scratching and staring at the 90% fold I could get. Ultimately, 90% wasn’t “stable” enough for my taste - just a little floppy and more of a 2 handed grab when folded (one hand for forend, other hand for buffer tube). So, I cut the access port.

But, that holey stock has numbered days. I bought a replacement on Black Friday. It sits in wait next to the thread protector that will replace the sight. So, complete fold and unholey stock get added as soon as I get the optic mounted on a satisfactory platform.

Regarding required takedown access and buffer tube: I appreciate the chop the unused cap off the buffer tube and access from the rear strategy, but I think I prefer my access window for a few reasons. 1. Pushing a round stop in to align it to insert a cross pin can get fiddley without taking off my boots. With top access, my finger is there for the final manipulations to insert or remove the pin. 2. locating the crosspin holes on the buffer tube was facilitated by visual confirmation. If you go rear access, you will slip the buffer tube on blind trying to get the holes lined up. And, 3. I just don’t mind having one more metal stop between the bolt and my shoulder - I know the guy that did my cutting and fitting.

Regarding the folding sights: I think any I’ve seen will still prevent a complete fold. I know you are not in love with that latch bit that hates you back so you won’t miss it. But, we didn’t talk about whether you need it fold capable. Anything higher than the forend pic rail will impair the fold.


I used a Red Lion Precision front sight. Dont have the MCarbo rear sight. Even with the fold down sight you will still need to cut into your stock and buffer tube. If you kept the stock front sight it’s so tall it would pass all the way through the buffer tube. Only way I can see to avoid this would be to just eliminate the front sight and run a red dot on one of the mounts that fold out of the way.