1] The number of legal gun owners in the 'high gun states' vs the 'low gun states
2] The total number of guns in each area, and
3] The number of justifiable or self defense homicides vs the number of criminal homicides.
It seems to me that that info would be relevant. For instance, if the 'high' states own 25 or 50 times the number of guns as the 'low' states, then 4 times as many gun deaths doesn't make gun ownership as significant a factor. The number of justifiable homicides would also seem to make the case that gun ownership is a positive factor rather than negative.