No data available that supports the idea there is a need for high capacity magazines

[billh58]

8. Another NRA Gun Myth (Talking Point)

Myth #6: Carrying a gun for self-defense makes you safer.

Fact-check: In 2011, nearly 10 times more people were shot and killed in arguments than by civilians trying to stop a crime.

• In one survey, nearly 1% of Americans reported using guns to defend themselves or their property. However, a closer look at their claims found that more than 50% involved using guns in an aggressive manner, such as escalating an argument.

• A Philadelphia study found that the odds of an assault victim being shot were 4.5 times greater if he carried a gun. His odds of being killed were 4.2 times greater.

http://www.motherjones.com/politics/2013/01/pro-gun-myths-fact-check

Actually, higher magazine capacity just increases the odds of being shot with your own gun