"Last year, Colorado conducted about 20,000 background checks on private sales both inside and outside gun shows. About 450 were denied."  OK,  so one out of every forty purchases is rejected. No information is provided on why they were denied.  How many of them were prosecuted?  Again, no information provided as context.  In this 2013 story, DP indicates that when a purchase is denied, and the denial is appealed,  58% of the denials are overturned.  http://www.denverpost.com/2013/01/31/fed-data-colorado-gun-background-check-system-among-tightest-in-u-s/