[phillmv]

I think the argument goes, the more weapons out there period the easier it is for people to smuggle them into the hands of criminals.

You can't just build a handgun in your basement; you need a tool and die machine, know-how, etc. In other words, a factory.

If you live in a state where it's relatively easy to buy a handgun and the registration requirements are limited and so on, you're going to find it a lot easier to procure one on the black market than say, here in Canada where you need to take a course and file a report every time you want to take it out of your house.

[Symmetry]

Making a modern semi-automatic requires some expertise, but making a zipgun that can shoot a bullet or two and is accurate enough to hit someone in the same room as you isn't that hard. http://en.wikipedia.org/wiki/Improvised_firearm

[talmand]

I've always felt the difference in attitudes towards guns in Canada versus the US is more about culture then it is about laws.

[doktrin]

Culture tends to impact laws, but that wasn't the parent's point.

The general availability of a given product in a given area affects said products availability in said area's black market.

In this case, more guns in circulation = more guns on the black market. This isn't to say that all black market guns originated from the legal (market), but supply does trickle down.