Except that they didn't. NICS checks by year from 1998:
1998 - 892,840 (Nov and Dec only)
1999 - 9,138,123
2000 - 8,543,037
2001 - 8,910,191
2002 - 8,454,322
2003 - 8,481,588
2004 - 8,687,671
2005 - 8,952,945
2006 - 10,036,933
2007 - 11,177,335
2008 - 12,709,023
2009 - 14,033,824
2010 - 14,409,616
2011 - 16,454,951
2012 - 19,592,303
2013 - 21,093,273
2014 - 20,968,547
2015 - 23,141,970
2016 - 27,538,673
2017 - 25,235,215
2018 - 15,128,636 (through July - on track for 25,934,805 if numbers hold)
Grand total - 293,581,016.
So, 2016, 2017, are higher, and 2018 is set to be higher, than all years from 2015 back to 1998.
Source: https://www.fbi.gov/file-repository/nics_firearm_checks_-_month_year.pdf/view
There is also a state-by-state list - https://www.fbi.gov/file-repository/nics_firearm_checks_-_month_year_by_state.pdf/view
My point was that they will find a way to avoid the truth no matter what.