As lawmakers in Washington, D.C., consider President Obama's proposal to institute a new assault weapons ban, we thought it would be helpful to take a look at the last one.

What was the 1994 assault weapons ban?

The law banned the manufacture, transfer, and possession of certain semiautomatic assault weapons (otherwise known as simply “assault weapons” or “AWs”). The law applied to several named weapons, as well as any semiautomatic pistol or weapon that has “an ability to accept a detachable magazine” and at least two of five specific features listed in the law.

It also banned the transfer or possession of “large capacity ammunition feeding devices” (otherwise known as “large-capacity magazines” or “LCMs”). These were defined as “a magazine, belt, drum, feed strip, or similar Device”…”that has a capacity of, or that can be readily restored or converted to accept, more than 10 rounds of ammunition; but does not include an attached tubular device designed to accept, and capable of operating only with, .22 caliber rimfire ammunition.’’

Officially known as Title XI of the Violent Crime Control and Law Enforcement Act of 1994, the ban went into effect on Sept. 13, 1994. It was repealed 10 years later.

Did the ban have any major limitations?

According to the 2004 National Institute of Justice Assessment of the ban, it had one big one: Assault weapons and large-capacity magazines manufactured before the effective date of the ban were “grandfathered” and thus legal to possess and transfer. That’s a whole lot of firepower:

In 1990, there were an estimated 1 million privately owned assault weapons in the U.S. that would have been grandfathered.

in the U.S. that would have been grandfathered. Americans possessed an estimated 25 million guns equipped with large-capacity magazines in 1994, and gun industry sources estimated that -- including aftermarket items for repairing and extending magazines -- there were at least 25 million LCMs available in the U.S. as of 1995, with at least 4.7 million pre-ban LCMs imported into the U.S. during the ban.

Has anyone measured the ban’s effectiveness?

The Law Enforcement Act of 1994 required a study by the U.S. attorney general to determine the effects of the ban, to be conducted within 30 months after it was enacted. The National Institute of Justice awarded a grant to The Urban Institute for an evaluation, which was titled “Impact Evaluation of the Public Safety and Recreational Firearms Use Protection Act of 1994.” That evaluation was updated in 2004 by one of the original authors (findings below). Since the ban was allowed to lapse in 2004, there hasn’t been another comprehensive national study.

What was the criminal use of assault weapons before the ban?

According to the 2004 assessment mentioned above:

By most estimates, assault weapons were used in less than 6 percent of gun crimes before the ban (about 2 percent in most studies and up to 8 percent in others). The relatively small number can be attributed to the higher cost of AWs and the fact that longer AW’s are difficult to conceal. Most of the AW s used in crime were assault pistols rather than assault rifles.

were used in less than 6 percent of gun crimes before the ban (about 2 percent in most studies and up to 8 percent in others). The relatively small number can be attributed to the higher cost of AWs and the fact that longer AW’s are difficult to conceal. Most of the s used in crime were assault pistols rather than assault rifles. Guns equipped with LCMs — of which AWs are a subset — were used in roughly 14 percent to 26 percent of most gun crimes. Although this range was based on a small number of studies, it is generally consistent with national survey estimates stating that approximately 18 percent of all civilian-owned guns and 21 percent of civilian-owned handguns were equipped with LCMs as of 1994.

What were the effects of the ban?

According to the official NIJ assessment:

The share of gun crimes involving AWs declined by 17 percent to 72 percent for the locations observed in this study (Baltimore, Miami, Milwaukee, Boston, St. Louis, and Anchorage) during all or some of the 1995-2003 post-ban period. This is consistent with patterns found in national data on guns recovered by police and reported to ATF.

declined by 17 percent to 72 percent for the locations observed in this study (Baltimore, Miami, Milwaukee, Boston, St. Louis, and Anchorage) during all or some of the 1995-2003 post-ban period. This is consistent with patterns found in national data on guns recovered by police and reported to ATF. However, in the jurisdictions studied, the decline in AW use was offset throughout at least the late 1990s by steady or rising use of other guns equipped with LCMs . The failure to reduce LCM use has likely been due to the immense stock that was in place prior to the ban as well as imports, the report found.

use was offset throughout at least the late 1990s by steady or rising use of other guns equipped with . The failure to reduce use has likely been due to the immense stock that was in place prior to the ban as well as imports, the report found. The few available studies do, however, suggest that attacks with AWs and other semiautomatics equipped with LCMs result in more shots fired, more people hit, and more wounds per victim than do attacks with other firearms.

What is the trend in crimes involving assault weapons since the ban’s expiration?

As explained above, there has been no comprehensive nationwide study done since 2004. However, the Police Executive Research Forum reported several findings in "Guns and Crime: Breaking New Ground by Focusing on the Local Impact" in 2010. Since the ban’s expiration in 2004: