Not sure what the "sequential declines" refers to, as the "adjusted" checks are up. Here are a couple of posts from a gun blog today (sales are only looking bleak in the future because they can't maintain inventory to meet the increased demand):
http://extranosalley.com/?p=85837“We can’t Get Glocks, and the closer to election it gets, the worse it gets"
I stopped by my favorite gun dealers to see if by accident they had a Glock 37, to hear the counterman say, sadly, “We can’t get Glocks right now, and the closer to election it gets the worse it gets.”
Yes, many Americans are afraid that the gun ban party will put Clinton or Sanders in the White House and the Democrats will regain control of the House and Senate.
So Americans are buying new guns are a rate more than four times the 20th century average, and would buy far more if they were available.
and
http://extranosalley.com/?p=85839New Record, More Than 2.5 million NICS Checks In March
The FBI reports a new record for the number of NICS checks for March of 2,523,265 National Instant Criminal Checks. That tops the previous record of 2,488,842 in March of 2014.
The total for the first quarter of 2016 is 7,682,141 NICS checks, and the total would likely be over 10 million for the quarter if the manufacturers could make them that fast.
The supply of new guns is almost non-existent, and popular guns are going for well over MSRP.