Mendoza HM-3

Lore & Background

The HM-3 is a lightweight submachine gun designed for compactness, achieved by extending the wrap-around bolt forward around the barrel. A grip safety is provided to prevent accidental discharge. The stock is designed for easy folding and unfolding and serves as a foregrip when folded. The selector lever is located on the right-hand side, allowing operation by the right hand without releasing the weapon. The stock can be folded or unfolded while gripping the weapon with both hands, unlike previous models. The magazine is located on the grip.

Three 9mm variants exist: the HM-3-S LONG (15.74 in, used by Mexican Police and state/municipal security forces), the HM-3-S SHORT (12.99 in, with a shortened barrel), and the HM-3-S BULLDOG (10.8 in, designed for motorcycle police and bodyguards). All 9mm versions may use 20- or 32-round magazines. In 2024, the HM-7-C and HM-7-L models in 9mm Parabellum with a 20-round magazine were introduced to the U.S. civilian market through Mendoza Firearms LLC in Tomball, TX; these come standard without a stock, resembling a pistol.

Since 2011, a .380 ACP variant has been produced, the largest caliber available to private security companies and individuals in Mexico. The .380 HM-3-S LONG is called "COBRA .380" and the HM-3-S BULLDOG is called "BULLDOG .380." All specs match the 9mm models except caliber and magazine capacity: .380 models carry a 35-round magazine.

Reader's Guide

The Mendoza HM-3 represents a notable entry in submachine gun design from Latin America, specifically tailored to the needs of Mexican security forces and the civilian market. Its compact layout, achieved by the wrap-around bolt, allows for a short overall length without sacrificing barrel length, making it suitable for close-quarters use by police, motorcycle patrols, and bodyguards. The folding stock that doubles as a foregrip and the ambidextrous-friendly selector lever (operable without releasing the weapon) reflect practical design choices for rapid deployment and one-handed operation. The introduction of .380 ACP models in 2011 addressed legal restrictions in Mexico, where that caliber is the largest permitted for private security and personal defense, and the marketing names "COBRA .380" and "BULLDOG .380" helped distinguish these consumer-oriented variants. The 2024 U.S. civilian release of stockless HM-7 models further expanded the weapon's reach, adapting it to a pistol-like form factor. The HM-3's legacy lies in its adaptation to specific regulatory and operational environments, demonstrating how a single platform can be modified for different markets—from law enforcement to private security to civilian ownership—while retaining core features like the grip safety and compact design.

Did You Know?

• The HM-3-S BULLDOG is also called the HM-3-S Mini and was designed for motorcycle police and bodyguards.
• Since 2011, .380 ACP models of the HM-3 are available, with the LONG variant named 'COBRA .380' and the BULLDOG named 'BULLDOG .380'.
• The HM-7-C and HM-7-L models, introduced in 2024 for the U.S. civilian market, come standard without a stock.