The FX-05 Xiuhcóatl assault rifle is México’s indigenously designed and manufactured assault rifle. It is used exclusively by the Mexican armed forces and national guard. Xiuhcóatl is Náhuatl for turquoise serpent. Náhuatl is an indigenous (Aztec) language spoken in central parts of México. It is estimated that there are about one and a half million Náhuatl speakers today. In the case of the FX-05 assault rifle, Xiuhcóatl is translated into “fire serpant”.
The assault rifle was first seen in public on September 16, 2006 during the Mexican Independence Day celebrations. It was carried by members of the elite assault team, the Grupo Aeromóvil de Fuerzas Especiales (GAFE).
Manufacturing of the weapon began in 2005 after a design period that lasted about 16 months, according to government records. The Mexican military deployed 65 military engineers on the Xiuhcóatl project as part of a program to reduce the costs modernizing the inventory of troop weapons.
The assault rifle was developed by the Dirección General Industrial Militar Mexicana (DGIM), the Mexican military’s manufacturing arm. The Mexican government first proposed making its own weapons during the 2003 national budget allocations.
The assault rifle was designed specifically to meet the Mexican requirements of its troops. The designers considered the Mexican arm reach of the typical Mexican soldier. The weapon includes a cold-forged barrel, folding stock and uses an interchangeable magazine with 30 rounds each. A 100-round drum is also available. The ammunition used by Xiuhcóatl is the is the 5.56x45mm NATO round (FMJ SS109). It has a rate of fire of 750 rounds per minute. It is constructed of a carbon-fiber polymer with a corrosion resistant steel action. The rifle comes in dark-green and desert bronze.
Since 2006, there is a pending patent (PA/A/2006/007961) application before the Mexican Patent authority for the Xiuhcóatl. According to the Secretaria de Defensa Nacional (SEDENA), the weapon cost $91,304,796.73 Pesos (about $8 million USD at the 2007 exchange rate) to design, including the raw materials, the machinery and the necessary infrastructure according to government documents dated January 31, 2007. 
The Mexican government explained that it undertook the design of the weapon to “reduce the costs associated in the fabrication of weapons for the military, increase the firepower of the military and give the soldier tactical superiority”. The Mexican government also noted that the North Atlantic Treaty Organization or NATO had adopted, as its second official round, the 5.56x45mm round, the same used by the Mexican assault rifle. 
A short time after the Mexican military deployed its new weapon in 2006, the German company Heckler & Koch (HK) declared that the Mexican weapon was a pirated copy of the company’s G36.  Heckler & Koch had expected to sign a licensing agreement with the Mexican government to manufacture its G36 in México and equip Mexican troops with it. However, the Mexican government determined it was less expensive to design and manufacture their own assault rifle then pay the licensing fees.
According to the periodical, La Jornada this accusation resulted in the dismissal of the director of the Mexican military industry directorate, General Alfredo Oropeza Garnica. After a thorough inspection by the German company, Heckler & Koch acknowledged that the Mexican assault rifle was not a pirated copy.  SEDENA also declared that there was no pending legal action against General Juan Alfredo Oropeza Garnica, exonerating him. 
By designing and manufacturing within México, the Mexican armed forces has been reducing the cost of its weapons programs in addition to providing the Mexican military greater autonomy.
The Mexican government has said that the Xiuhcóatl costs about $10,000 Pesos to produce, a substantial reduction in the cost to make the HK G36 under license. The Mexican military has the capacity to manufacture 30,000 rifles annually but has only been making 15,000 each year.
According to Janes Defense, by 2005, the Mexican military had produced about 44,000 Xiuhcóatls. The Mexican military planned to replace its inventory of about 121,000 HK G3’s rifles by 2018. By 2019, the Secretaria de Defensa Nacional (SEDENA) announced that it had produced 165,000 rifles.
There are three versions of the weapon, full-length rifle, a carbine and an urban assault weapon. The length of the barrel is the main difference between the variants. The rifle is ambidextrous.
The name, FX-05 is short for Fusil Xiuhcóatl 2005.
1. Response to Mexican Open Records Request no: Record no: 0000700010707.
2. Response to Mexican Open Records Request no: Record no: 0000700109506.
3. Pedro Miguel, “Opinión: El regreso de la xiuhcóatl,” La Jornada, May 17, 2007.
4. Mark Rutherford, “The case of the copycat fire serpent,” c/net News, March 13, 2007.
|Length:||Assault Rifle||1,087 mm (42.8") extended stock|
|887 mm (34.9") folded stock|
|Carbine||980 mm (38.6") extended stock|
|780 mm (30.7") folded stock|
|Machine gun||1,244 mm (49") stock extended|
|1,0244 mm (41.1") folded stock|
|Sharpshooter||1,204 mm (47.4")|
|Width:||56 mm (2.2")|
|Weight:||Assault Rifle||3.89 kg (8.6 lbs.)|
|Carbine||3.22 kg (7.1 lbs.)|
|Machine gun||4.23 kg (9.3 lbs.)|
|Sharpshooter||4.02 kg (8.9 lbs.)|
|Cartridge:||5.56x45 mm NATO (OTAN)|
|Rate of fire:||750 rounds per minute|
|Muzzle:||920 m/s (3,018 ft/sec)|
|Range:||200-800 meters (218-874 yards)|
|Has Picatinny railing|
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