When did Obama say that?
He said something similar in December 2008, before being sworn in.
http://www.suntimes.com/news/politics/obama/1318968,obama-gun-sales-up-120808.article
He also discussed it sometime in February 2009.
It was a while back, but I found it.
http://www.suntimes.com/news/politics/obama/1318968,obama-gun-sales-up-120808.article
Obama: Don’t stock up on guns
ABDON M. PALLASCH Chicago Sun-Times December 8, 2008
As gun sales shoot up around the country, President-elect Barack Obama said Sunday that gun-owning Americans do not need to rush out and stock up before he is sworn in next month.
I also found another good reference...
The article that appeared in the Chicago Defender on Dec. 13, 1999, when Obama was in the Illinois state Senate. According to the Defender, at an anti-gun rally, Obama "outlined his anti-gun plan," which, among other things, sought to "increase the federal taxes by 500 percent on the sale of firearm, ammunition [sic] -- weapons he says are most commonly used in firearm deaths."
Factcheck.org asked the Obama campaign about his position on an ammunition tax but have received no response.
The claim "Close Down 90 Percent of Gun Shops in America" also is based on the 1999 Defender article. It reported Obama was pushing "all federally licensed gun dealers sell firearms in a storefront and not from their homes while banning their business from being within five miles of a school or a park." The NRA states that the 5-mile limit would have resulted in the closing of 90 percent of gun shops in the country.
Again, Factcheck.org asked the Obama campaign about his position on an ammunition tax but have received no response.