Here's a CNN story on a drug smuggling tunnel, running underneath the US/Mexican border.
Why am I bringing this up?
Whenever I tell people that criminals will go to great ends to supply the black market whatever it demands, they tend to not fully comprehend exactly how serious these people take that "job".
People who crush up hundredsds or even thousands of pills, preforming lengthy extractions on them to get the PSE out (main precursor for the production of methamphethamine), who rip the striking pads off from just as many matchbooks to get red phosphorous for the recuction are obviously willing to put a lot of work into their criminal schemes, provided that there's money to be made.
This drug bust is no different. Half a million dollars worth of drugs, that's a pretty good incentive to get digging, wouldn't you agree?
All to circumvent prohibition program that's been around for half a century, which has consumed vast amounts of resources, imprisoned and killed people, both criminals and innocent people.
And people try to tell you that criminals wouldn't set up underground gun factories? Sure, most criminals can use a bat or edged weapon equally well as a firearm, but if there's still a demand (gang wars, serious robberies, defending that .5 million worth of drugs from other people, ...), you can bet your buttocks that illegally produced guns would start turning up. Anything from simple break action shotguns to fully automatic submachineguns have been made by unskilled civillians over time, just look at the history of the STEN machine gun if you don't believe me.
An aspiring spree killer deprived of guns could learn how to build explosive devices that are just as likely to kill a large amount of people as a shooting spree would be. And some would think they wouldn't? Deranged nutcases who are dedicated to having their 15 min of glory by killing others before taking their own life, or being killed by the police aren't going to say "gee wiz, I can't get a gun, guess I'll just go have myself commited then".
Stop underestimating thee people, both the professional criminals and the mentally ill.
If you don't, it could come back to haunt you.