Mexico has, count them, ONE gun store in the entire country. It’s run by the Mexican Army and, if you want to buy a gun, you have to fill out the paperwork, jump through their hoops, and then go to that gun store, at their convenience, and buy your gun at a 100% mark up from MSRP. The process takes about a year to navigate, and very few people outside of the hunting guides and some rich people bother. According to the Huffington Post, in 2013 there were over 22,000 homicides in Mexico, the majority committed with firearms.

THAT is how your plan will work.