AR15 6" Handguard: Keymod & Picatinney

thingiverse

I made quite a few changes to the originnal design. After shortening the modular design to ~6 inches, I printed it and it felt too flexy for my taste. I also noticed the barrel nut had no lip, it was threads for like twice the distance needed, so nothing would hold a barrel in place (I noticed and corrected this prior to printing). This version of the barrel nut is a merge between the original thing's barrel nut exterior and the interior of one I had which threaded on and did its barrel-holding job correctly. I've also filled the through-holes in and added dimples for M6 set screws. I've put gas-tube grooves in all 4 flats, so your barrel nut can be tightened down to the nearest 90 degree increment. Lastly, I've added 4 edge-notches since I'm obviously using printed lowers, and needed to beef up the material around the takedown pin, so I needed a little extra clearance around that area. The hadguard itself is just 2 of the original keymod rails on the sides, and original picatinny rails on the top and bottom, but all shortened to 6 inches. I've filled in the gaps to make a solid piece. The old through holes are gone, replaced by four M6x1.0 tapped holes for set screws. You can actually print those if you want, I'll add some to this project later. I've given about 0.2mm of clearance around the barrel nut, so expect a snug fit. This is by design, but it should fit if you push hard enough. I notched one edge of one picatinney rail, that is intended to be the bottom near the front takedown pin. I had to shave a little of the lip inside the barrel nut (at the end of the treads) to get it to hit my desired snugness at just the right amount of twist to line up correctly. Otherwise, screw on your barrel nut, slide the handguard over it, and clamp it in place with 4 set screws. I printed my hanguard vertically, (I didn't want picatinny rail sections to pop-off at a layer weld, so it seemed better for strength). If you want to print vertically, use the version with a support tree, It's separated from the handguard by an air-gap and will pop off the same way a raft does. Print it without supports, as my supports have everything under control. If you want to do your own thing with orientation, use the non-support-tree version.