Or because (1) the mechanisms for enforcement are weak at the state level, (2) because you're not controlling for other factors that increase crime and (3) the fact that massive gun violence has a direct causal link to more gun laws, you could reject the idea of state stats based on their "gun laws" being very meaningful and look at national stats, for example:

http://www.realclearscience.com/blog/gunsnosa.jpg

How about a useful state stat:

http://www.motherjones.com/files/gun-ownership-vs-gun-deaths...