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

[Kaleva]

11. A letter Bill Ruger sent to every member of Congress

"The best way to address the firepower concern is therefore not to try to outlaw or license many millions of older and perfectly legitimate firearms (which would be a licensing effort of staggering proportions) but to prohibit the possession of high capacity magazines. By a simple, complete and unequivocal ban on large capacity magazines, all the difficulty of defining 'assault rifle' and 'semi-automatic rifles' is eliminated. The large capacity magazine itself, separate or attached to the firearm, becomes the prohibited item. A single amendment to Federal firearms laws could effectively implement these objectives."

http://en.wikipedia.org/wiki/William_B._Ruger#Controversy