Correction: Mexico is awash in MACHINE GUNS, GRENADES, as well as ANTI-PERSONNEL and ANTI-ARMOR ordnance(claymores, RPGs, etc.).
The one legal gun store in Mexico is only allowed to sell pistols under 9mm (.38 super OK), shotguns, and single-shot rifles for hunting. It is located in Mexico City, and you must travel there in person to file all of the paperwork required, and be there in person to pick up both your approved paperwork and the firearm in question. For each firearm, there is a separate transaction.
Aside from the military-grade weapons and ordnance used indiscriminately by the government and the cartels against Mexican citizens, Mexico is a gun-control “Brady Paradise”(TM).