[7][8] The rifle was officially presented in the military parade on September 16, 2006, in the hands of the Special Forces Airmobile Group, GAFE (Grupo Aeromóvil de Fuerzas Especiales).

[14] On September 16, 2016, the Mexican military unveiled a new variant of the FX-05 known as the Xihucóatl Submachine Gun alongside an indigenous underbarrel grenade launcher made for it.

Most of the rifle's receiver is constructed of a polymer reinforced with carbon-fiber with an underlying titanium frame and comes in black, dark-green and desert-tan colors as well as the SEDENA digital camouflage patterns used by the Mexican army.

The charging handle can be installed on either side of the rifle with gas piston located above the barrel, which operates under a multi-lugged rotary bolt system.

On February 1, 2007, representatives of the SEDENA (Secretaría de la Defensa Nacional) and Heckler & Koch met in Mexico City to address accusations of patent infringement from the German firm.

After an exhibition of detailed models of the FX-05, the HK representatives were convinced that, despite the similarities between the two rifles, there was not a patent infringement, therefore bringing an end to the disagreement.

Either way it appears that the newer post lawsuit versions of the FX-05 feature a different newly designed receiver, as the newer FX-05 come with a four position fire selection (safe, single shot, three round burst, full auto) whereas the original FX-05 came with only three firing selections (safe, single shot, full auto).

This theory is also reinforced by the fact the new black FX-05 models feature a visible metal protrusion before the magazine ejector and the receiver is noticeably smaller.