On Mexico

The BBC, like many other new organizations, recently ran an article about the ongoing drug-related violence going on in Mexico.
In the article, a particular quote stood out to me:

Mexico’s gun laws are tight, but in the US it is far easier to get weapons. The Mexican government says lax US gun laws help arm the cartels and fuel the violence.

While US gun laws are far less strict than Mexico, I seriously doubt that the US is responsible for most of the weapons being used by the drug cartels. While I won’t say that US-sourced weapons haven’t been found in Mexico (they clearly have), I’m saying that the bad guys are getting most of their weapons from other sources. The ATF seems to agree.
First off, straw purchasing — where someone buys a gun for a prohibited person, which is illegal — doesn’t scale well. It’s one thing for a gang member to get his girlfriend to buy a gun or two, but it’s a different thing entirely for drug cartels to hire enough straw purchasers in cities all over the country to buy hundreds of thousands of guns and get them over the border without being noticed. It’s made worse when gun stores are routinely out of popular semi-auto guns like AR-15s and AK variants which, the news organizations claim, are the guns being smuggled.
Secondly, why would the cartels risk such high-level detection by straw purchasing from gun shops in the US? US gun dealers are regulated by the ATF, all retail purchasers must undergo FBI background checks, fill out forms, etc. Cars crossing the border are routinely searched for contraband. Seems like a lot of hassle for a marginal gain. It’d be far easier for the cartels to bribe Mexican military members or port authorities to overlook a container or two of smuggled arms than to buy guns — where they’re available — at retail prices in the US.
Thirdly, many of the guns being found in Mexico are machine guns, not their semi-auto lookalikes commonly available in the US. Machine guns are tightly regulated in the US and usually quite expensive. Legal, transferable M16s in the US tend to cost in excess of $12,000 and require both local and federal approval for purchase. Since the registry for privately-owned machine guns was legislatively closed in 1986, the number of legal machine guns has remained constant (or possibly declined slightly, as guns are damaged, destroyed, stolen, etc.). With actual machine guns being so expensive and uncommon, it would be incredibly unwise for the cartels to attempt to smuggle American-owned machine guns into Mexico.
With some skilled machine work, one can convert semi-auto guns into full-auto guns (doing so would be considered making a post-1986 machine gun, and it is generally illegal for private citizens to make or own such a conversion), but again this has problems scaling. Converting a gun or two is plausible, but converting enough guns to arm hundreds of thousands of cartel members? Unlikely, considering the number of machinists and equipment needed to do so.
Fourthly, Mexico has numerous porous borders, whether it’s the large amounts of relatively unpatrolled shoreline or the border with Guatemala. Why would cartels risk detection smuggling arms over the US-Mexico border when they could simply smuggle arms from other sources into the country by land or sea? Bribing a port official to let a container of guns in isn’t that hard, nor is unloading one’s own ships (whether with smaller boats onto a beach somewhere, or into a cove).
Fifthly, the cartels pay a lot more than the Mexican police or military does, so it wouldn’t surprise me at all if guns were given or sold to the cartels from police or military armories. Since the US often trades, legally, in arms with Mexican government authorities, this may be why captured guns are being traced back to the US.
Sixthly, there are numerous international arms dealers and nations who would gladly exchange arms for currency. Why risk the wrath of the US government when the cartels could simply buy from a willing foreign government or dealer by the containerload?
Basically, I’m applying Occam’s Razor here: it’s far more simple and plausible that the cartels are getting their guns from the Mexican police and military, from international arms dealers, or from another state (say, Venezuela) than them buying machine guns at vastly inflated prices in the US or straw-purchasing semi-auto guns and then converting them to machine guns.
Unsurprisingly enough, the news media doesn’t consider this (or if they do, they don’t print it), preferring to parrot the same story over and over. The ATF says it isn’t happening. Border Patrol says it isn’t happening. Why, then, does it keep coming up again and again?