There are a lot of reasons someone would want to fire 30 rounds without reloading

[jazzimov]

34. How about Australia and the UK?

Objective: To determine whether Australia’s 1996 major gun law reforms were associated with changes in rates of mass firearm homicides, total firearm deaths, firearm homicides and firearm suicides, and whether there were any apparent method substitution effects for total homicides and suicides.
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Results: In the 18 years before the gun law reforms, there were 13 mass shootings in Australia, and none in the 10.5 years afterwards. Declines in firearm-related deaths before the law reforms accelerated after the reforms for total firearm deaths (p = 0.04), firearm suicides (p = 0.007) and firearm homicides (p = 0.15), but not for the smallest category of unintentional firearm deaths, which increased. No evidence of substitution effect for suicides or homicides was observed. The rates per 100 000 of total firearm deaths, firearm homicides and firearm suicides all at least doubled their existing rates of decline after the revised gun laws.

Conclusions: Australia’s 1996 gun law reforms were followed by more than a decade free of fatal mass shootings, and accelerated declines in firearm deaths, particularly suicides. Total homicide rates followed the same pattern. Removing large numbers of rapid-firing firearms from civilians may be an effective way of reducing mass shootings, firearm homicides and firearm suicides.

http://injuryprevention.bmj.com/content/12/6/365.full

In the United Kingdom, firearms are tightly controlled by law,
.....
The United Kingdom has one of the lowest rates of gun homicides in the world. There were 0.07 recorded intentional homicides committed with a firearm per 100,000 inhabitants in 2010, compared to the 3.0 in the United States (over 40 times higher) and 0.21 in Germany (3 times higher).
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In 2012 the Home Office reported that, "in 2010/11, firearms were involved in 11,227 recorded offences (statistics limited to England and Wales), the seventh consecutive annual fall".

http://en.wikipedia.org/wiki/Gun_politics_in_the_United_Kingdom

OH, I'm sorry - you said ONLY assault weapons. Maybe Obama really SHOULD "take away" everyone's guns!