Tossed some numbers around with a shop in town today, I would need to produce 50-100 in a single run to come in at anything resembling a competitive price point. I have a couple other options to explore yet, once I have determined the best bet I'll see what I need to do to set up a group buy or something along those lines. Not looking to make a ton of $$$ off of this, honestly just wanted a better stock adapter haha.
DIY 3D Printed XCR Stock Adapter!
- Thread starter BeerBaron
- Start date
Alright, so the group buy was a no go, deemed a business activity.
The PVC model held up to light use, however any side-side flexing resulted in cracks starting at the base of buffer tube threads. The 100% infill version I'm sure would hold up to anything I would ever do to a rifle (I try and take pretty good care of my stuff...) but dropping it off a quad or something like that I feel could possibly break the stock adapter, so I wasn't completely happy with the strength.
After doing a little more research on 3D Printing, Nylon seemed like a much better option for this part. I got back online and found someone local to print a nylon version for me.
Nylon Pros:
- MUCH better layer adhesion. I believe an injection molded ABS part would have been strong enough, but my 3D printed examples suffered failures between the layers as opposed to the material itself breaking.
- More flexible vs ABS. Don't take this to mean the part is rubbery, its quite rigid. What this does mean though is in the event your stock were to take a sharp blow, where the ABS would crack, the nylon will flex slightly and return to its original shape.
- Printed much closer to my modeled dimensions. I had to adjust some of the dimensions by up to 25 thousandths on the ABS part, the Nylon was within 5 thou almost everywhere.
- Can Dye the nylon any colour you like.
Nylon Cons:
- Flexible. Obviously a completely rigid part would be ideal so while this helps the durability/toughness, its a con as well. I honestly wasn't able to detect any flex handling/shooting the rifle with this adapter, so not a big deal.
- Prints a translucent off-white colour. I didn't take any pictures before dying my part, and while I'm not super picky on appearance, this colour was a no go haha. As you can tell from the pictures, even though I dyed the part black, it has a bit of a translucent blue look to it. I am going to try some different paints/coatings on this one and see if I can get the appearance closer to the XCR/Buffer tube, however I'm not sure how easy it is going to be to get something to adhere to Nylon. If anyone has any recommendations on this point I'd love to hear them.
As I alluded to before, I shot 80 rounds with this stock adapter attached this afternoon without even a hint of an issue. Compared to the ABS this nylon is TOUGH. Tough enough that I am likely not going to bother putting further effort into getting one machined. If someone out there is dying to make me one in aluminum (for a reasonable cost... CNC was far too expensive to just make one piece) I would love to hear from you, but otherwise I'm confident this one will survive way more abuse than I will ever put it through, and if it doesn't a new one is cheap and easy to make. The only way I can see this breaking is with some extreme side to side bending/prying action, certainly not from normal shooting/carrying of the rifle.
Some improvements I have made include taking about 1/4" out of the added LOP compared to my original design (I have a final copy being printed right now that will reduce it even further) as well as adding a radius to the back of the internal buffer tube threads to help lessen the stress concentration in this area. Attachment is achieving using a modified 1/4" x 1 1/4" stainless bolt and nut recessed into the adapter. I was not confident in printing working 1/4" threads to use the OEM stock attachment bolt, so this seemed like a good option. I had to turn down the head of the bolt to 3/8" diameter to match the stock bolt and clear the upper receiver and recoil buffer. Enough blabbing, here's a couple more pictures...
The PVC model held up to light use, however any side-side flexing resulted in cracks starting at the base of buffer tube threads. The 100% infill version I'm sure would hold up to anything I would ever do to a rifle (I try and take pretty good care of my stuff...) but dropping it off a quad or something like that I feel could possibly break the stock adapter, so I wasn't completely happy with the strength.
After doing a little more research on 3D Printing, Nylon seemed like a much better option for this part. I got back online and found someone local to print a nylon version for me.
Nylon Pros:
- MUCH better layer adhesion. I believe an injection molded ABS part would have been strong enough, but my 3D printed examples suffered failures between the layers as opposed to the material itself breaking.
- More flexible vs ABS. Don't take this to mean the part is rubbery, its quite rigid. What this does mean though is in the event your stock were to take a sharp blow, where the ABS would crack, the nylon will flex slightly and return to its original shape.
- Printed much closer to my modeled dimensions. I had to adjust some of the dimensions by up to 25 thousandths on the ABS part, the Nylon was within 5 thou almost everywhere.
- Can Dye the nylon any colour you like.
Nylon Cons:
- Flexible. Obviously a completely rigid part would be ideal so while this helps the durability/toughness, its a con as well. I honestly wasn't able to detect any flex handling/shooting the rifle with this adapter, so not a big deal.
- Prints a translucent off-white colour. I didn't take any pictures before dying my part, and while I'm not super picky on appearance, this colour was a no go haha. As you can tell from the pictures, even though I dyed the part black, it has a bit of a translucent blue look to it. I am going to try some different paints/coatings on this one and see if I can get the appearance closer to the XCR/Buffer tube, however I'm not sure how easy it is going to be to get something to adhere to Nylon. If anyone has any recommendations on this point I'd love to hear them.
As I alluded to before, I shot 80 rounds with this stock adapter attached this afternoon without even a hint of an issue. Compared to the ABS this nylon is TOUGH. Tough enough that I am likely not going to bother putting further effort into getting one machined. If someone out there is dying to make me one in aluminum (for a reasonable cost... CNC was far too expensive to just make one piece) I would love to hear from you, but otherwise I'm confident this one will survive way more abuse than I will ever put it through, and if it doesn't a new one is cheap and easy to make. The only way I can see this breaking is with some extreme side to side bending/prying action, certainly not from normal shooting/carrying of the rifle.
Some improvements I have made include taking about 1/4" out of the added LOP compared to my original design (I have a final copy being printed right now that will reduce it even further) as well as adding a radius to the back of the internal buffer tube threads to help lessen the stress concentration in this area. Attachment is achieving using a modified 1/4" x 1 1/4" stainless bolt and nut recessed into the adapter. I was not confident in printing working 1/4" threads to use the OEM stock attachment bolt, so this seemed like a good option. I had to turn down the head of the bolt to 3/8" diameter to match the stock bolt and clear the upper receiver and recoil buffer. Enough blabbing, here's a couple more pictures...
'Final' version with a Magpul UBR installed! Shortened up about as much as I dare go, and a little more detail added to the profile. I managed to get the dye to take a little better on this one with a higher temperature... it was definitely black this time, though still shiny. Tried some plain old flat black krylon camo paint on it and it actually stuck much better than I expected! I am pretty much unable to scratch it off without using a metal tool. I may considering printing another if I can find someone local to print in Taulman Alloy 910 Nylon as its supposed to be about twice as strong as what this one is printed in (Taulman Bridge), and less flexible, though this one will more than meet my requirements.
looks good. it wouldnt be hard to machine from alu if you want to get rid of some of the aesthetic shapes to cut down on machining time.
I ran into the same issues you ran into when i first designed my SKS XCR mag adapter 2.5 years ago. High costs unless making large quantities, no guarantees people will buy even a lot of "i'd take one...." was posted. Lets not even go into CGN's hand out before a single actual product has been made.
In the end, you have the satisfaction of creating something that fits you specifically and works great!
I ran into the same issues you ran into when i first designed my SKS XCR mag adapter 2.5 years ago. High costs unless making large quantities, no guarantees people will buy even a lot of "i'd take one...." was posted. Lets not even go into CGN's hand out before a single actual product has been made.
In the end, you have the satisfaction of creating something that fits you specifically and works great!
