Rafael Mendoza immediately became involved in the Anti-Reelectionist cause and fought in three battles as an infantryman under the leadership of Pancho Villa.

Mendoza responded with a bolt-action, single-shot design with a short barrel and simple metal sled that could be moved easily by two men or carried on horseback.

To operate the action, the user rotated the pistol grip outward and backward to unlock the bolt, extract and eject the case.

After more prototypes and military trials in 1931 at Rancho del Charro, D.F., Mendoza’s design was officially adopted in 1934 after being demonstrated to President Cardenas personally.

The "Fusil Ametrallador Systema Mendoza" Model 1934 is an air-cooled, magazine-fed, gas-operated light machine gun weighing approximately 18.5 lb.

While Hector studied drafting at the University of Detroit, Rafael traveled the U.S. making arrangements to manufacture the guns ordered.

When World War II ended in September 1945, the U.S. Government canceled most arms contracts, including those for Mendoza, before any guns could be delivered.

This new model emphasized ease of production and eliminated the quick-change barrel, cooling fins and flash hider.

Productos Mendoza made approximately 50 prototype Model RM2 machine guns which were subsequently tested by the Mexican Marine Corps, but not adopted.

As the Mexican constitution expressly forbids the export of "instruments of war," Mendoza was handicapped by having his designs restricted to one potential customer: Mexico.

During the late 1940s, Mendoza also began development of a submachine gun in 9 mm Luger, .38 Super Auto and .45 ACP caliber.

Feeling that military arms were too narrow a base for the company, Hector focused on the commercial market for .22 rimfire rifles.

Almost immediately Mendoza’s domestic market for rimfire rifles ended, and most of the 500 Mexican gun stores closed their doors.

That enabled the company to survive, and today Productos Mendoza continues to offer office products, bicycle parts and air rifles.

Called the HM-3, the new submachine gun is blowback-operated, of all-steel construction and feeds from a 32-round detachable magazine inside the pistol grip.

Multiple safeties, solid construction and quality manufacture have earned Productos Mendoza substantial orders from the Mexican Government for the HM-3.

The RM2 is the most recent model and adds a simplified method of stripping, by simply removing a lock pin, the stock and rear of the receiver can be folded down to allow the bolt and piston to be withdrawn backwards.

It had a fixed smooth barrel with a slash-cut slotted muzzle brake, simplified gas cylinder, different front and rear sights, less-raked handguard / foregrip, separate handguard and buttstock assemblies, side-mounted sling swivel on the left side just above and behind the pistol grip, and a straight sided magazine.

The RM2 was made shortly after World War 2 and chambered for the .30-06 US (7.62×63mm) ammunition, which was adopted as the new standard by the Mexican army during the late 1940s.