andyt andyt:
Just go to a gun show, and away you go.
Indeed. If you're lucky enough to be a resident of a US state that uses the instant background check system then, yes, you can go to a gunshow and buy a gun and leave with it. And why not? If you pass the background check then what's the difference where you buy your gun?
But if you live in a state with a waiting period you cannot leave the gun show with the gun. While you might buy it at the gun show you'll have to wait the required waiting period and then go pick it up at the gun shop.
Gun shows anymore are highly regulated and aggressively patrolled by Federal, state, and local law enforcement and if you're going to obtain a gun illegally then a gun show that's crawling with uniformed and undercover cops is probably not the best place to do it.

For a Canadian the least difficult way to obtain such a thing is by courier. It's pretty amazing what comes into your country (and mine) from Russia and China almost every day of the week.

You can't inspect them all.