I find it easier to deal with the anti's if I can show them my facts, then ask them to show me theirs.

Return to “Myth: 40% of Guns Sold w/o Background Check”
the number comes from a 251-person survey on gun sales two decades ago, early in the Clinton administration. More than three-quarters of the survey covered sales before the Brady Act instituted mandatory federal background checks on February 28, 1994.
<snip - Read the link for the facts>
We don’t know the precise number today, but it is hard to believe that it is above single digits.