Note the why is very important here. My hypothesis is that guns from Gun friendly places being funneled into Gun Control places. A solution would be banning all guns to decrease the amount of gun deaths. This, however, is not a practical solution politically for various reasons.
It's not a practical solution, full stop. See how mass quantities of drugs are smuggled around the world; guns and the small supplies of ammo criminals use (they aren't big on practicing) are much more compact, durable etc.
Not a good analogy. People want guns because other people have guns. But people do not want drugs because other people have drugs
Some people want to buy drugs to do drugs with other people and to fit in. If their friends or whoever didn't do drugs they may not buy drugs themself.
Some people want to own guns to go hunting by themself and would still want to do it even if nobody else owned guns.