"All kinds of restrictions or bans" can mean a lot of things, but for the sake of looking into your theory, let's check out a couple basic factors like having Shall Issue CCW and state-level Assault Weapons Bans. Here are the 10 most dangerous cities for 2012, in order from worst to least, and status of the shall issue and AWB laws for those states.
Detroit, MI - Shall issue, no state level AWB.
St. Louis, MO - Shall issue, no state level AWB.
Oakland, CA - Restrictions/bans.
Memphis, TN - Shall issue, no state level AWB.
Birmingham, AL - Shall issue, no state level AWB.
Atlanta, GA - Shall issue, no state level AWB.
Baltimore, MD - Restrictions/bans.
Stockton, CA - Restrictions/bans.
Cleveland, OH - Shall issue, no state level AWB.
Buffalo, NY - Restrictions/bans.
Forbes article on 2012 most dangerous cities.
Of course there other various restrictions we could look at. For example, in the #2 city of St. Louis, state law says that loaded car carry is okay in the vehicle without a permit, yet even with this relatively liberal gun law they still wound up the second most dangerous city in America. By contrast, noticeably absent from the list are Los Angeles, New York, and Chicago, each of which is in a state with some of the nations most restrictive gun laws. Bottom line, it appears that "most gun related crime" does
not come from these cities. Quite the contrary, most of the cities that made the list are in shall-issue CCW states with no restrictions on magazine size.