URX 3 and 3.1 side and bottom picatinny rails set for M4 AR15 AK and others

thingiverse

Recently I got my hands on a URX 3 style barrel cover and I'm absolutely thrilled with its performance in every aspect. However, I soon found myself struggling to find picatinny rails that match this system perfectly. Keymod and M-Lok are not fully compatible, which made things tricky. So, I decided to take matters into my own hands and reworked a keymod set to make it fit the URX guard. The URX 3 requires 40mm of space between screws, with the screws having an outer diameter of 6mm and a head size of 10mm. Fortunately, my rifle came with all the necessary screws, but if you don't have them, you'll need to drill holes for the screws and their heads by hand - it's not a big deal, just take your time and drill slowly. To accommodate printer inaccuracy, I reduced the rail width from 21.2mm to 20.8mm and the height from 6mm to 5.8mm. Since the URX design provides ample space below the rail, you should have no problem fitting a mount. When printing these rails, use 8-10 layers for the bottom, 5-8 layers for the perimeters, and 5 layers for the top. For the infill, opt for a honeycomb pattern with 30-40% rectilinear fill density - this will give you a smooth finish on top. If your print comes out a bit rough, don't worry; just sand it down to smooth out the surface.