As I have mentioned before, gun control and the US Second Ammendment is one of my areas of interests.
This post from PJ Media has an interesting comparison between US and Canadian murder rates from states/provinces that border each other.
While this is an interesting comparison, I don't think the relationship of less restrictive gun control = less crime is proven in this comparison. Florida has liberal carry laws, but I suspect its murder rate is higher than most Canadian provinces.
I think that popluation density, rural vs urban living may have more of an effect on murder rates than gun control.
This is not to say that gun control does not have an effect. Most location experience a drop in their violent crime rate when it is easier for law abiding citizens to get a gun.