If magazine were limited to 10 round even rampage killers would no be able to cause as much death and destruction as they have because they have to reload.
As of June 2013, 4233 people have been killed by guns. The Southeast, which has relatively looser gun laws, contributes 37% (vs. the Northeast, which is more densely populated and all contributes 17%). Using the US mortality data from the World Health Organization, researchers calculated that approximately 185,866 years have been stolen (so far in 2013 alone).