Realistic 5.56mm Ammo Belt

This is a realistic model of a 5.56x45mm NATO ammo belt with M27 links, as used in the M249 Squad Automatic Weapon, FN Minimi, HK MG4, and many others. It is the perfect accessory to cover the bb feeding tube on airsoft LMGs, or for display. This model was designed from measurements taken from actual 5.56mm rounds and M27 links. While I don't have access to a belt-fed machine gun to verify the dimensions of the links, the rounds themselves feed and extract properly in an actual rifle. Please note that this test was performed to verify dimensional accuracy - these models are inert and cannot be converted into live ammunition.

The model is separated into 3 pieces to minimize reliance on multimaterial systems and reduce waste. The M27 link should be printed in matte black, the shell casing in a gold or brass color, and the bullet in a copper color. I used Bambu Matte Charcoal and Overture Silk Gold and Silk Copper. For M193/M196 (Vietnam-era ammo), the bullet should be solid copper, with a red tip every 5th round. For M855/M856 (Desert Storm/GWOT era ammo), each round has a green tip, with a red tip every 5th round (as pictured in the images above). The most modern ammo is M855A1/M856A1, which has slightly different bullet geometry, but can be approximated by coloring the tips grey, with red every 5th round. The bullet in both the .3mf file and the print profile has been pre-split for coloring, but the same effect can be had by printing the bullets in a solid color then dipping approximately 6mm of the tip into the correct color paint.

If you desperately need more color, the primer (the inner circle on the base of the shell casing) can be colored silver. Some rounds utilize silver primers, and some match the shell casing's color. There's no “most realistic” answer here, so print what looks cool! That being said, I did not split this part for coloring, so you'll have to color paint it yourself should you so desire.

This has been a rare example of a model where the small size made it easier to work with. The assembled belt has roughly the same flexibility as the real deal, and due to the size, the links seem to hold up well with minimal stretching. The bullets on my print friction-fit well, but a drop of glue may be required based on the tolerances of your printer. If you're going to be running around with this, I would also recommend gluing the double-link end of the links to the shell casings - this will ensure they stay in place without affecting the flexibility of the belt. Just be aware that the thin rim retaining piece on the double link end is fragile due to the print orientation, so don't put too much pressure on it while you're removing supports.

My print profile uses 3 walls for the links, which makes them solid for maximum strength. I recommend 5% grid infill and 2 walls for the shell casings, which minimizes material usage but still supports the opening for the bullet properly. Due to the geometry of the bullet, it requires no infill at all - however, I would recommend printing multiple bullets at once to avoid print failures due to short layer times at the tip.

Please remember that this can be mistaken for real ammunition, so be smart in how you use it. Don't do anything illegal, and always be kind!

As always, please like or boost if you like this model. I work pretty hard on these, and it brings me joy seeing other people printing and enjoying them. Please post pictures if you print it and like it! I hope you enjoy!