AR-15 Grip and Stock in Print

So the first part of the AR-15 grip and stock combined part has printed successfully.  An initial prototype revealed some design flaws made by my altering the geometry of the grip itself by angling it back 15 degrees from normal.  

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Way too thick to wrap my hand around. and that thumbhole is just too small.  In the corner you can see an aborted print.  It had some missed Y steps and the hot-end jammed.  I tend to set-it-and-forget-it with my printer, so when a hot-end jams, i’m pretty much not there to catch and fix it in time to save the print.  I get my filament at less than $10 a pound, so i’m not overly worried about the wasted parts(that’s about half what most places charge for it) and on small parts the cost is fairly negligible.  I think this whole part was under $3, and it’s one of the biggest ones i’ve ever made.  It is absolutely the first to be 100 mm tall.  I wasn’t sure my X carriage would clear the frame, but it did(barely!) 

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Here is the updated part on the bed.  

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and here it is next to the two-part lower.  I haven’t cleaned the support from the main body of the lower, nor installed the parts kit. 

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And here is all of it next to the previous attempt at printing an AR-15 lower.  You can’t see it in this picture, but that is the broken lower which I mentioned in a previous post.  

I have FI this weekend(which i still haven’t prepared for) so don’t expect too much progress on this too soon.  Clearing the support material from the AR lower is a delicate task, and I’d like to do some acetone brushing to clean up the sides, as I’m fairly certain this one is a keeper.  

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5 Responses to AR-15 Grip and Stock in Print

  1. Have Blue says:

    I tested my own printed lower a bit last night after cleaning and lubricating the .223 upper (which had been giving me feed and extraction issues even with a proper commercial lower). While my .223 upper is now running great with a commercial lower, I’m still having feed/extraction problems with the printed lower. I’m almost positive that this is due to to the buffer tower bending slightly during recoil of the BCG, which causes the bolt carrier to drag in the buffer tube.

    As such, I think your use of a thumbhole buttstock to support the buffer tube from underneath (and not just relying on the strength of the buffer tower) is going to be the best method for running a printed lower. I’ll need to do a little FEA to see if printed ABS alone might still be able to work if the buffer tower is beefed up some more.

    • turomar says:

      check out the version 6 files for the grip-and-stock i uploaded to thingiverse. Now it fits the A2 stock, and works with large hands.

      • Have Blue says:

        Any chance you might be able to post original CAD files for the grip-and-stock? I ask because I understand our Kiwi friends can have AR-15s (if properly licensed), but only if they have a thumbhole buttstock on the rifle. Since the Bell & Carlson thumbhole buttstocks are no longer made, such items are a desired commodity, and if they could make them indigenously in New Zealand, no annoying import laws will interfere

  2. wayshwing says:

    Hey guys,

    I’m an engineer and gunsmith, having built over 30 custom AR15’s for clients. I have been experimenting with printed ABS lowers (for educational purposes only of course).
    I have seen issues with both the buffer tower and the front takedown pin bosses. I have seen both crack both during use and during transport. I have also had the bolt release mounting boss crack as well, most likely from side impact during transport in a soft guncase.
    As for the bolt release and front takedown pin bosses, I’m bolstering up those sections. I’ll be forming slots to allow me to bond in steel support plates for the takedown pin bosses, and I’m thickening the bolt release bosses. As for the buffer tower, I’m adding side bosses, which will allow me to permanently attach the steel rear receiver plate to the buffer tower, using flathead screws (that will be flush with the receiver plate), and cyanoacrylate.

    • Have Blue says:

      Even with beefed up bolt release bosses, mine still split from the roll pin – I’m now a proponent of just gluing a plain dowel pin into place, as it’s worked great for me with no cracking.

      I’ll be trying vacuum bagging carbon fiber over the front takedown bosses and buffer tower to stiffen/strengthen those areas.

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