The issue of stockpiling ammunition has been raised in the aftermath of Wednesday's deadly mass shooting in San Bernardino, California. Authorities said the husband and wife who carried out the attack fired 75 rounds, killing 14 people, before fleeing. They had more than 1,600 bullets with them when they were killed and well over 4,500 rounds of ammunition at their home, police said. Investigators haven't explained how they acquired the bullets.
Here are a few questions and answers about regulations involving ammunition purchases:
WHAT ARE THE LIMITS ON AMMUNITION SALES?
Four states — Massachusetts, New Jersey, Illinois and Connecticut — require a license for ammunition purchases, and a background check is required to obtain a license, according to the San Francisco-based Law Center to Prevent Gun Violence.
But there are no federal restrictions on the volumes of ammunition sales, and there is no national system for tracking ammunition purchases.
"I don't know how the government would decide what amount would be appropriate," said Lawrence Keane, senior vice president and general counsel for the National Shooting Sports Foundation.
Keane said the volume of bullets found in the San Bernardino shooters' possession shouldn't raise any eyebrows.
"Those are not substantial quantities if you're a target shooter," he said. "You can go through several hundred rounds on a weekend at a shooting range."
HAVE THERE BEEN PREVIOUS EFFORTS TO REGULATE AMMUNITION SALES?
Gun control advocates pushed for limits on ammunition sales after the 2012 massacre at a Colorado movie theater by a gunman, James Holmes, who legally purchased thousands of bullets from online retailers. Their efforts largely fizzled.
Wednesday's mass shooting in California could fuel a renewed campaign to restrict ammunition sales, but activists on opposing sides of the debate aren't forecasting a different outcome.
U.S. Rep. Bonnie Watson Coleman, D-New Jersey, filed legislation in May that would restrict online ammunition sales. Similar measures filed by two other Democrats after the Colorado shootings went nowhere.
"I don't know what it's going to take for us to move on some of this common-sense legislation," Watson Coleman said. "This is a very difficult Congress."
ARE THERE ANY OTHER PENDING EFFORTS TO LIMIT AMMUNITION SALES?
In October, a group of gun safety advocates led by California Lt. Gov. Gavin Newsom launched a ballot campaign that could make the state the first to require background checks for ammunition purchases at the "point of sale."
"What happened in San Bernardino underscores the need to look closely at who is buying ammunition, and that is something that is addressed by the initiative," said Lindsay Nichols, a senior attorney for the Law Center to Prevent Gun Violence, which helped craft the ballot measure.
After the deadly 2012 shooting at a Connecticut elementary school, New York enacted a law that called for developing a database for ammunition background checks. Gov. Andrew Cuomo, a Democrat, suspended the requirement in July after state police determined the technology needed for the database doesn't exist.
IS IT UNUSUAL TO HAVE THOUSANDS OF ROUNDS OF AMMUNITION STORED?
An attorney for family members of shooter Syed Farook says no.
"As a gun owner myself, I myself probably have four or five thousand rounds of bullets that I keep at home," Attorney David Chesley said at a news conference Friday. "And the reason why you buy them in bulk is because they're cheaper that way.
"And the government keeps on outlawing different types of bullets and different types of guns at different times. And then there'll be shortages of bullets that occur very commonly where Homeland Security will order 2 million of a certain kind of bullet and you can't get that bullet, it's not available for many months.
"So especially if you are target shooting it's not at all uncommon to own 2,000, 3,000, 4,000 rounds to have with you — when you can get them at a cheap price you stock up."