No carbines doesn't mean it is made for civilians. All it means is a 16" barrel or less. Law Enforcement, military, and civilians all use carbines. It's a moot point. If you don't believe me go to a gun board and ask.
How is manufacturing your own weapons cost less? Well, if an AK cost $500 each, the cost to smuggle the weapon into Mexico, danger of getting arrested, and fees for the buyers. Which is cost effective, produce it in Mexico/Latin America for $50 each or buy it from the USA?
If you go to Youtube you will find many videos where drug gangs use fully automatic weapons against the police. Those weapons didn't came from the USA.
If the serial number is grind off how can they said it came for the USA?
If you bought a gun from a FFL it is log into the book. Then you sell it to a private individual it, it doesn't log into the book. That is correct.
However, what the Mexicans are saying is that ten of thousands of arms are coming to their country from the USA. That means they needs ten of thousands of straw buyers to not be trace back. Do you think out of those straw buyers that none of them would rat on the Mexicans? If one straw buyer bought over 1000 guns and all of them landed in Mexico, would that be easy to find out by the ATF?
Disregard the propaganda in the video. Notice the primitive tools these kids use to make firearms? Making firearms isn't hard. It's very simple. American kids graduate out of high school without any trade skills whatsoever. Hence you got a lot of people thinking that firearms needs a magic wand and a clean room to produce. There are many videos floating around the net. This video is well known, tho.
http://rpginn.com/index.php?option=c...=365&Itemid=39
Don't me started with Yeman. Yeman has the largest ratio of gun per person in the world. Every villages produce their own weapons.