[SlapHappyPappy]

The whole notion of the US being a major source of firearms is absurd. Ammunition possibly, but not firearms.

First, the weapons causing the most problems are legal only with an FFL. Smugglers are unlikely to want a paper trail of their desire to acquire fully automatic weapons.

Additionally, the weapons can be purchased easily in any number of other countries at prices much lower, and quantities much higher, than would be available in the US. The cost differential would more than overcome the additional shipping costs involved.

[freeandfreezing]

You are right. The agents themselves know it too:

“I do not believe we can even make a dent in (southbound smuggling) because that assumes the cartels are complete idiots, which they’re not. Why in the world would they try to smuggle weapons and currency through a checkpoint when there are so many other options?” said Border Patrol Agent T.J. Bonner, president of the agents’ union.

According to CBP, between March 12 and April 30 officers seized:

—Fifty-one pieces of ammunition, weapons parts and guns..

--from the article.

[William Tell]

SlapHappyPappy said: "Ammunition possibly, but not firearms."

I doubt that. How about providing an estimate of the total number of rounds fired by criminals in Kalifornia last year? Was it even a thousand? Two thousand?

I would be surprised if Kalifornia's criminals used more ammunition last year than I have in my house. Ammunition will never be scarce to criminals.