The FX-05 Xiuhcoatl is the standard service rifle of the Mexican Armed Forces, replacing the earlier Heckler & Koch G3 from 2008 onwards. It is a selective-fire assault rifle that has an external resemblance to the Heckler & Koch G36 series. In fact it resembled the G36 so much that Heckler & Koch brought suit against them due to perceived industrial espionage and copyright infringment. The internal workings of the FX-05 were proven to be different but its exterior looked too much like the G36. The Second Generation version in production from 2007 onwards was therefore redesigned with a different-looking pistol grip and receiver than the H&K G36 series due to this perceived infringement on Heckler & Koch's brand.
The 6.8x43mm SPC wildcat round was considered during its development, but was dropped in favor of the more standardized 5.56x45mm NATO round. The Sharpshooter variant may still chamber the 6.8mm SPC.
It comes in Assault Rifle, Assault Carbine, Short Carbine, Sharpshooter, and Light Machinegun variants. Nearly all use a side-folding adjustable stock that folds to the right and has a combination carrying handle / integrated optical scope that attaches to a Picatinny rail on the top of the reciever. The fixed forend has a picatinny rail along its top, a short accessory rail for bipods and lights along its bottom and has attachable rails on its sides. The Sharpshooter variant has a fixed adjustable stock, the Machinegun variant has a quick-change heavy barrel with bipod, and the Short Carbine variant has a shorter forend. The weapon and its accessories come in Black, Dark Green and Desert Tan, as well as a series of camoflauge finishes.
Its proprietary 30-round magazines are not STANAG-compliant, but are supposedly STANAG-compatible. They are semi-translucent, but the magazine base and follower come in the same colors as the weapon. The magazines come with integral lugs (like that of the SIG SG-550 series) to allow them to be fitted together like they were clamped to aid in speedloading.
The FX-05 Short Carbine is called the FX-08.