The AR-15, which was used in the Sandy Hook School shooting, is "America's most popular rifle,” in part because it is "is customizable, adaptable, reliable, and accurate," according to the National Rifle Association . One of the guns used in the Orlando shooting was an AR-15 style semi-automatic rifle.Florida has some of the nation’s most lenient laws when it comes to gun sales. While a three-day waiting period is required by the state, background checks are not required when guns change hands between private parties. The state also does not limit the number of weapons that can be purchased at one time or regulate “unsafe handguns” or large capacity ammunition, according to the Law Center to Prevent Gun Violence.A person living in Florida is usually only prohibited from having a firearm if the person is convicted of a felony or is a "violent career criminal," as defined by law, according to the Law Center to Prevent Gun Violence. Likewise, there is no requirement under federal law to prohibit a person on a watch list from buying a weapon.Last year, the FBI ran background checks some 23 million times, according to the U.S. Government Accountability Office. But nationwide, individuals who were on a terrorist watch list who tried to buy a weapon were able to do so almost all of the time, the GAO found. In 2015, while people on the terrorist watch list were routinely checked, some 91% of the time they were allowed to proceed with a firearm purchase, according to federal data . Transactions were denied only 21 times — out of 244 firearm-related background checks.