began to develop the AR-15 (AR meaning "ArmaLite," not "assault rifle").
1959: The first year the AR-15 was manufactured by Colt.
M-16: The automatic infantry rifle design based on the AR-15.
4,299,551: Guns manufactured in or imported to the U.S. in 2001.
9,162,924: Guns manufactured in or imported to the U.S. in 2009.
50: States in which AR-15-style rifles are legal.
2.5 million: AR-style rifles sold between 1986 and 2010, according to National Rifle Association reports.
30: Percentage of AR-15 owners who purchased their first rifle in 2009 or 2010.
519: AR-15 models on the commercial market in 2011.
12,626: Deaths by firearms in the U.S. last year.
323: Deaths by rifles that year.
28: People killed in shooting sprees last week in the U.S. with AR-15-style rifles.
30: Most rounds that can be held in a standard magazine. Larger magazines can hold up to 100 rounds.
10: Most rounds a magazine may legally hold under gun-control legislation proposed by state Sen. Ginny Burdick (D-Portland).
0: Restrictions on semiautomatic rifles in Oregon.
30: Minutes in which Oregon State Police must complete a background check on a person buying a gun—or provide an estimate of how much longer it will take.
$10: Fee for that background check. A buyer must provide full name, address and an Oregon driver's license.
60: Percentage of AR-15 owners who own more than one of the rifles.
35: Percentage of AR-15 owners who first owned a paintball gun.
44: Percentage of AR-15 owners who have military or law enforcement backgrounds.
$1,083: Average price, with accessories, of AR-15s purchased new in retail stores.
$436: Average amount an AR-15 owner spends on after-market accessories.
8/10: Proportion of AR-15 owners who say they weren't able to fire their guns as much as they would have liked in the past year.
7,000: Gun manufacturers that are members of the National Shooting Sports Foundation, a gun lobbying group and defender of the AR-15.
06470: ZIP code of the National Shooting Sports Foundation, based in Newtown, Conn.
2.7: Distance in miles from the National Shooting Sports Foundation's headquarters to Sandy Hook Elementary School.
SOURCES: FBI; U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives; National Rifle Association; National Shooting Sports Foundation; Shooter's Bible Guide to AR-15s; Google Maps