I don't care why either have lower rates. Just like you don't care about the Harvard study. 
Riddle me this Batman
The Harvard study attempts to answer the question of whether or not banning firearms would reduce murders and suicides. Researchers looked at crime data from several European countries and found that countries with HIGHER gun ownership often had LOWER murder rates.
Russia, for example, enforces very strict gun control on its people, but its murder rate remains quite high. In fact, the murder rate in Russia is four times higher than in the “gun-ridden” United States, cites the study. ”Homicide results suggest that where guns are scarce other weapons are substituted in killings.” In other words, the elimination of guns does not eliminate murder, and in the case of gun-controlled Russia, murder rates are quite high.
The study revealed several European countries with significant gun ownership, like Norway, Finland, Germany and France – had remarkably low murder rates. Contrast that with Luxembourg, “where handguns are totally banned and ownership of any kind of gun is minimal, had a murder rate nine times higher than Germany in 2002.
The study found no evidence to suggest that the availability of guns contributes to higher murder rates anywhere in the world. ”Of course, it may be speculated that murder rates around the world would be higher if guns were more available. But there is simply no evidence to support this.”
Follow the bouncing ball
The study found no evidence to suggest that the availability of guns contributes to higher murder rates anywhere in the world. ”Of course, it may be speculated that murder rates around the world would be higher if guns were more available. But there is simply no evidence to support this.”
I don't care about the Harvard study? Then why did I quoted that study twice?

I don't know the exact murder rate from each European country (prob, like 99.99% of us..), just like the exact gun ownership laws. For example, what are the similarities between the Norwegian & the U.S. gun law, and what are the differences? In other words, how easy/hard is it to obtain a gun in both countries?
I find it interesting that the murder rates in the U.S. are significantly higher than all European countries, except Russia. I'm not surprised about Russia, that's a fucking corrupt state.