Much has been written about two studies of the 1994 Assault Weapons Ban by former Urban Institute researchers Chris Koper and Jeff Roth. Much of it is wrong.

In 1997, the Urban Institute published the results of the first study of the 1994 Federal Assault Weapons Ban (Roth and Koper 1997). The first study was a short-term follow-up that found the law had little effect on assault weapon purchases. However, this was not evidence that a ban on such weapons would be ineffective. Rather it noted shortcomings in the law, itself:

• The law, as enacted, grandfathered all assault weapons manufactured prior to the ban, meaning such weapons could be legally possessed;
• There were large increases in assault weapons sales prior to the Ban taking effect, further exacerbating the effects of the grandfather clause; and
• Hundreds of thousands, if not millions, of guns that were manufactured prior to the Ban were legally imported into the US during this period.

Because the study was limited statutorily to a brief follow-up period, none of these factors had worked through firearms markets at the time the first study was completed.

Clarifying the 1994 Assault Weapons Ban

The second study by the same researchers was published at University of Pennsylvania (Koper, Woods and Roth 2004) and showed the Ban’s broader effects on violence over time. These two federally funded studies are by far the most comprehensive tests of the effects of the Assault Weapons Ban.

Before describing those results, we should clarify what the goals of different parts of the legislation were. The two main provisions of the bill — a ban on weapons with at least two military style features, and a ban on large capacity magazines — have been misconstrued in today’s debate.

Then, as now, military-style assault weapons were rarely recovered from street crimes and large reductions in street violence were not expected to result from the Ban. However, assault weapons were (and are) disproportionately more common in mass shootings and shootings of law enforcement officers.

At the same time, the ban on large capacity magazines was intended to have a more direct effect on street crime, since as much as a quarter of gun crimes involved a weapon, generally an automated pistol,  with a large capacity magazine.

Finally, it’s important to note that the federal requirement that a weapon have two features causing it to resemble a military-style assault weapon meant that it was relatively easy for manufacturers to re-engineer a weapon to comply with the law without fundamentally changing the firearm.

For instance, Intratec, the manufacturer of the Tec-9, simply changed the barrel of the Tec-9 and renamed it the AB-10 (“After Ban”) to comply with the law. Thus, unlike New York’s SAFE Act which bans weapons with a single military-style feature, the 1994 federal law prevented the sale of relatively few firearms.

Measures and Findings of the 2004 Study of the Assault Weapons Ban

The 2004 study used three measures to examine the effects of the Ban:

• Was the market place for assault weapons and large capacity magazines altered such that prices increased and production decreased?
• Were fewer assault weapons and large capacity magazines used in the commission of a crime? And,
• Were the consequences of use less severe (i.e. Were there fewer murders and injuries)?

Major findings of the law on assault weapons:

• Effects of the Ban on assault rifles is inconclusive with respect to prices and production;
• Prices of assault pistols were increasingly higher than comparable handguns;
• Production of assault pistols declined much faster than comparable handguns;
• The number of recovered assault weapons declined by 70 percent between 1992-1993 and 2001-2002 (from 5.4% to 1.6% of recovered weapons that were traced by The Bureau of Alcohol, Tobacco, Firearms and Explosives at the request of local law enforcement.);
• Throughout most of the post-ban period (particularly 1995 to 2001), the share of assault weapons among weapons recovered from crime scenes declined, as assault weapons traces either increased less or declined more than total traces (Table 6-1, columns 2 and 3), a pattern that is also consistent with a decline in the use of assault weapons relative to other guns (Koper 1995: 44);
• Assault weapons’ share of crime guns declined between 17% and 72% when looking at all guns recovered in the following cities: Boston (72%), Miami (32%), St. Louis (32%), Baltimore (34%), Milwaukee (17%) and Anchorage (40%) (range of dates, mainly compares early 90s to early 00’s):

Major findings of the Assault Weapons Ban on large capacity magazines:

• Prices of large capacity magazines increased 80 percent from 1993 to 1998. This price increase was for primarily for magazines used in assault pistols, not assault rifles;
• The use of large capacity magazines in crimes is more difficult to study as ATF does not trace large capacity magazines. However:
  • In Baltimore, large capacity magazine gun recoveries were 24% lower in 2002-03 than in 1995 (this is almost entirely due to a large reduction in large capacity magazines for pistols);
  • In Anchorage, large capacity magazine handgun recoveries were 16% lower in the 1995-2002 period when compared to 1992-1993;

Studies have also consistently found that more shots are fired when a semi-automatic pistol is used than when a revolver is used.  In mass shootings, and average of 29 shots are fired in automatic weapon/large capacity magazine cases compared with 15 in non-automatic weapon/large capacity magazine cases.

Finally, when a large capacity magazine is involved in a gun crime, there is a higher probability of a shooting victim. This may be due either to the discharge of more rounds or a greater tendency on the part of someone with a large capacity magazine to shoot it.

The 1994 Assault Weapons Ban had important, positive effects. Those effects were just beginning to take root when the Ban expired in 2004. Given the trends shown in the data, if the Ban had been reauthorized in 2004, today’s debate would be about whether to extend the Ban again next year. And, even with the very limited restrictions it put in place, the data used to inform that debate would almost certainly show important declines in violence.