A recent study published in the Harvard Journal of Law & Public Policy concluded that there is a negative correlation between gun ownership and violent crime in countries internationally (more guns = less crime).
Nations with strict gun control laws have substantially higher murder rates than those who do not in general. In fact, the 9 European nations with the lowest gun ownership rate have a combined murder rate 3x that of the 9 European nations with the highest gun ownership rate!
*Based upon Kleck & Gertz estimates of 2.5 million defensive gun uses per year (see source #2). A similar study in 1994 under President Clinton (Source) found this number to be 1.5 million, which would result in guns being used over 47x more often to defend a life than to take one.
According to the Bureau of Justice Statistics, about 436,000 crimes were committed with a firearm in 2008 (Source). This would mean guns are used 5.7 or 3.4 times (using Kleck or Clinton respectively) more often to defend against a crime than to commit one.
**Comparing violent crime between two countries can sometimes be difficult as each nation defines it differently.