-The number of rifle homicides declined 41% between 1998 and 2012. Rifle homicides per 100,000 people in the Unites States declined 48.5% in the same period of time.
-The number of shotgun homicides declined 52% between 1998 and 2012. Shotgun homicides per 100,000 people in the Unites States declined 58% in the same period of time.
Most firearm homicides are committed using handguns, not rifles or shotguns. The number of homicides committed with long guns is small, according to FBI data, the number of people killed by rifles and shotguns in 2012 was 625, compare this to:
-518 people murdered with blunt objects
-678 people murdered with hands/feet
-1,589 people murdered with knives
In my opinion, the evidence suggests that long guns, which includes "assault weapons", are not a serious threat to public safety. Also, their use in murder has been declining dramatically in recent years. Thus, the case for banning long guns is as strong and as weak as the case for banning knives, blunt objects, and hands/feet.
FBI Data: http://www.fbi.gov/about-us/
US Census data: http://www.multpl.com/