Background checks and the purchase forms can work, at least sometimes, and they do save lives.
This guy was reported by several of his classmates as being all kinds of suspicious, and was locked up for trying to illegally buy
AK-47s:
"
He bought two AK-47 from Van Wagenen guns in Orem last October. Orem
police discovered the alien registration number Yohannes gave the gun shop is false. He was arrested and a search of his room turned up an imported Russian rifle and a large amount of ammunition."
"His roommates say Yohannes was quiet and watched a lot of violent videos on the internet. They say they
heard him talk about planning to be involved in a mass shooting."
http://nazret.com/blog/index.php?title=ethiopia_student_arrested_for_buyi ng_gun&more=1&c=1&tb=1&pb=1
That's one potential columbine stopped. It took me exactly 2 minutes to find this article(mainly because i was browsing various guns stats in an article before it)
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This guy was an ex cop and straw purchaser arms-dealer who got 10 years. The charge they nabbed him for was Falsifying paperwork.
All those little yes/no boxes put his ass away for a decade.
http://www.usatoday.com/news/nation/2007-03-03-guns_n.htm