Literally meaning "turquoise serpent" but also carrying the symbolic significance "fire serpent," the Xiuhcoatl was a creature of Aztec mythology – thus it is a fitting moniker for the FX-05 Xihcoalt Mexican assault rifle that entered service with the Mexican Army in 2006.

The weapon was developed by the Dirección General Industria Militar Mexicana (Directorate of Military Industry) or DGIM, the Mexican military's industrial arm, to replace the German-designed Heckler & Koch G3, which was produced in Mexico under license. The FX-05 was gradually phased into Mexican Army and was first seen in the September 16, 2006, Mexican Independence Day celebration when it was carried by soldiers of the Grupo Aeromóvil de Fuerzas Especiales (GAFE), the Special Forces Airmobile Group.

The FX-05, which has been widely used in the Mexican Drug Wars since its introduction, is chambered for the 5.56x45mm NATO round. It is a selective-fire, gas-operated assault weapon that utilizes a rotating bolt and has a rate of fire of 750 rounds per minute. It has an effective range of 200 to 800 meters and is fed from a 30-round detachable box magazine or 100-round drum magazine. It is currently available in three variations that include a full-length rifle, carbine and short carbine, and these differ mainly by barrel length. All three versions are made of carbon fiber reinforced impact-resistant polymer and utilize a translucent magazine, and each is adaptable for left-handed shooters as the charging handle can be installed on either side of the weapon.

This Mexican-made assault rifle isn't without some controversy. The Mexican government and German-based H&K had some 20 years ago agreed to supply locally-produced versions of the H&K G36 that were built at factories in Mexico under license. For a number of reasons, the Mexican government decided to go another direction, deciding it made more financial sense to design, develop and produce a homegrown weapon instead.

From appearances, it looked similar to the H&K G36 – so much so that the German government and H&K accused Mexico of copying the G36V design, and even threatened to take the case international tribunals. Mexico took the threat seriously enough that soon after the FX-05 was first seen in use with the GAFE units that it stopped manufacturing the new rifle.

The head of the DGIM, General Alfredo Oropeza, was caught in the legal crossfire. He had been in line to become the next Secretary of National Defense but was passed over due to the matter. Yet, just some three months later in a meeting between H&K and the Mexican government it was determined that the FX-05 was not, in fact, a copy of the G36. How this came to be as been a matter of conjecture but in the end, the Mexican Army has ramped up production.

While the 5.56mm round of the FX-05 is less powerful than that of the 7.62mm round of the G36, it is more ideally suited to the close-quarters urban warfare being seen in the sadly still ongoing war on the drug cartels. It could take something as powerful as fire serpent to truly turn the tide in that struggle.

Peter Suciu is a Michigan-based writer who has contributed to more than four dozen magazines, newspapers, and websites. He is the author of several books on military headgear including A Gallery of Military Headdress, which is available on Amazon.com.