How do background checks on gun sales work?

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A central part of the gun legislation Congress is expected to take up this week is the idea of expanded background checks on gun purchases. But few Americans understand how background checks actually work.http://feeds.feedburner.com/~ff/rss/cnn_us?d=yIl2AUoC8zA</img> (http://rss.cnn.com/~ff/rss/cnn_us?a=loa6EQ8f7qw:Nb0FBxMj3R8:yIl2AUoC8zA) http://feeds.feedburner.com/~ff/rss/cnn_us?d=7Q72WNTAKBA</img> (http://rss.cnn.com/~ff/rss/cnn_us?a=loa6EQ8f7qw:Nb0FBxMj3R8:7Q72WNTAKBA) http://feeds.feedburner.com/~ff/rss/cnn_us?i=loa6EQ8f7qw:Nb0FBxMj3R8:V_sGLiPBpWU</img> (http://rss.cnn.com/~ff/rss/cnn_us?a=loa6EQ8f7qw:Nb0FBxMj3R8:V_sGLiPBpWU) http://feeds.feedburner.com/~ff/rss/cnn_us?d=qj6IDK7rITs</img> (http://rss.cnn.com/~ff/rss/cnn_us?a=loa6EQ8f7qw:Nb0FBxMj3R8:qj6IDK7rITs) http://feeds.feedburner.com/~ff/rss/cnn_us?i=loa6EQ8f7qw:Nb0FBxMj3R8:gIN9vFwOqvQ</img> (http://rss.cnn.com/~ff/rss/cnn_us?a=loa6EQ8f7qw:Nb0FBxMj3R8:gIN9vFwOqvQ)
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