[Chowwow]

While waiting on my 3d Printer to print some things, I took some time to design my own stock adapters for a 1913 rail and for the ACR folding stock. People who have been here for a while will know that a few people have made these adapters over the years, with the most recent designs from Lucky Irishman who appears to be withdrawing from the business. To fill that void, I've decided to make my own. While the ideas are similar, I didn't use any of Lucky Irishman's data to make these; just measurements and observations on what I've learned about these platforms. I would like to give credit to 3D print group AWCY? for releasing the CAD models of the ACR folding stock end to the public; this project was made much more easier thanks to their hard work.

My idea is to produce two options for each adapter. One, a full-featured, CNC-machined aluminum adapter that has QD sling points and threaded holes both to screw into the XCR lower and to screw in the sling loop in the original ACR folding stock. Machining the 1913 rail is very simple, however, I can't think of an easier way to machine the ACR folding adapter without having to invest in a 5-axis machine. The other, more tangible option now, is to produce simplified and affordable 3D printed adapters for people who need one right away and don't need special features. While they won't be metal, and you have to be weary of keeping them in a hot car approaching 140 degrees F, they will be made of the best material available and they are all very sturdy and simple to install.


CAD models for the ACR folding stock adapter:

CAD models for the 1913 adapter:

The ACR adapter fresh off the printer:

The 1913 rail adapter:

Support material removed:

The nice thing about the 1913 adapter is that it replaces the need for a pistol endcap or fixed stock adapter.

Both adapters have clearance holes so a 1" long, 1/4-20 thread screw can reach through and screw into a nut on the other end.

I still need to install these things onto my rifle and test them for strength. Will report back when I get the chance to do so. Eventually, I'd like to make stock adapters for a buffer tube extension (so you can use AR stocks on the XCR) and an adapter for the Magpul Zhukov stock (I'll need a Zhukov first). Any ideas or critiques are welcome.

 

[Chowwow]

Great work sir! Looks incredible and hopefully one day 3d printers and materials will match the strengths necessary for hard core use.

I tried 3D printing when COVID hit in 2020. Sadly I went with a cheap Chinese printer and probably was too ambitious for it's capabilities. I tried several filaments, from PLA to PETG and finally nylon.

What printer and materials did you use for this project?

If you look around the 3DP2A space, there is a lot you can do with the current tech, and new designs are pushing the bounds of what can already be done. A lot of the ideas I had thought of earlier in the year have already been met or made obsolete already, so it moves very quickly. I'd like to do more in this space but if I were paid to spend time making designs for various guns like I do for my regular job, I'd be a lot more productive.

The monster I'm using right now is the Creality CR-10 S5, currently the largest printer that you can buy in the market for $700, as far as I know. Following that, I bought nearly $700 in additional parts and an enclosure to get it to work consistently as it does now. I got it so I would not be limited on space for what I can print in the future; most popular printers like the Creality Ender 3 are not quite large enough to print the lower for the XCR, but the CR-10 S5 has been able to put them out on a regular basis. I was printing with a generic PLA for model prints, but for these latest prints I've moved on to Inland's tough PLA, where I hope to produce models that are not only accurate to CAD but strong enough to perform fitness testing and even field deployment. I've been printing on a bed heated to 60 degrees C, printing on a hot end at 230 degrees C, at 100% infill with 10% fill on the supports, and I've started to print with a brim on the supports to help the models adhear to the print bed and stop warping. The real trick to 3D printing is to fiddle around with your settings to get the results you want with the materials you are using. You'll have to do your research and use manufacturer recommendations to narrow it down.

 

[Chowwow]

Awesome. I had an Ender3 v2. Went through 3 motherboards on it and 2 hot ends, wanted to pull my hair out but I probably started too aggressively and expected too much.

I think I had a lemon. Definitely needed an enclosed space to prevent nylon warping. Even bases and different techniques didn't really solve it.

It sounds like you pushed yourself to far, too fast. I'm still getting acclimated with the materials and tools that I have; it's not perfect but things are working as intended. I worked on using one brand of filament and making my prints as consistent as possible by buying gantry levelers, and enclosure, vibration absorption feet, upgraded T-nuts and an upgraded bed heater. I highly suggest you get back onto the hobby and start small with PLA+ and work on each little thing at a time, before it's made illegal, lol. Honestly, people who think criminals are using 3d printers to get around firearms laws don't know what they are talking about; there is no criminal out there with the patience and money to get into this space who also lacks the self-control to want to enact violence with these things. It's much easier to buy or steal regular guns than it is to leave a large receipt trail of printer and metal gun parts and assembling them.

Onto the design of these adapters themselves, it's not too hard to edit these designs for prime time, but there is curiously little interest in these adapters so far both on here and reddit. Getting these in metal will be the most important goal for this project. I also recently purchased a Magpul Zhukov stock for cheap to make an adapter for that when I'm available, though I expect enthusiasm for that will just be as tepid. Until then, I'll keep working on these but they are not as urgent as the XCR lowers.

 

[Chowwow]

I confess my primary interest is in that space, and when I saw the time and effort 3D printing takes, and then what the material my setup supported, I decided it wasn't worth the effort at the time. I would need to invest in better equipment and possibly wait for the industry to catch up to consumer printing of items that stand up to abuse like modern metals and polymers in firearms today.

Having 3 young kids at the time also required me to limit my hobbies. Keep doing what you are doing however. Hopefully one day all this is still legal and we can print practically indestructible, real world tough parts.

With kids, I know how that feels! Once you get the system dialed in though, these machines just take care of themselves, just how I like it!

I argue the critical point with the tech is now; 3D metal sintering is going to take some time to be cheap and it will be messy, only for garage machinists in the future. Tinkering with your printer IS the hobby when you are messing with these cheap printers; once you get the file you want to print, it's just a matter of pressing "start" and waiting. If you want to skip all that crap and just get what you want printed, I suggest more expensive printers from Makerbot that are about ready out the box to turn plastic spools into art or tools; Makerbot's machines are what businesses and schools use to make reliable 3D prints with no messing around. They start at $1200 - $2000, but if you want to make your Creality or Prusa printer reliable and robust, you need to spend the kind of money on equipment that would get you a Makerbot printer anyway. If you got a lot of projects or ideas, that investment on the printer will pay for itself anyway.

 

[Chowwow]

I've redesigned the adapters to be a short as possible. The picatinny adapter is less than one inch long now, while the ACR adapter is a little over one inch.

Here's how the picatinny adapter looks attached to the lower. The adapters require a 1-1/4" long, 1/4"x20 screws and corresponding nut to secure it to the lower.

The length of the lower+picatinny adapter versus the AR-XCR lower. It's just a bit longer than the AR-XCR.

How the ACR adapter looks on the lower.

How the adapter looks like compared to the AR-XCR.

 

[Chowwow]

Those look much cleaner than the lucky Irishman ones!

Looks very sharp, @Chowwow!

Eh, there are typical imperfections that come with 3D printing on them; stringing, pitting, etc. If I do sell these out, I may need to sand and file them down a considerable amount. The thing is, with parts as relatively soft as these, they will tend to get marred easily anyway and they won't look "perfect" in little time. They do seem strong enough to serve their purpose and priced at a point where no one would cry about breaking one or two of these anyway.

I just got one and it looks much better than all the previous lucky Irish adapters I've seen here. The anodizing is black instead of that purple.

It wasn't just that, but the machining step-overs that gave them a stepped appearance. I suppose that wasn't a big deal and the parts were still functional, though most machinists I've worked with would go the extra little effort to make them appear as smooth as reasonably possible.