The metro areas of such cities are often more
restrictive, thinking they'll be able to eliminate the criminals coming out of the core city. They're also not really suburbs, unless you extend the term to cover places like Newark and the like.
Here is a study
by Harvard Law that the US Supreme Court cited in the Heller case, finding that gun restrictions often worsen the murder rate. Luxembourg, for example, has a complete gun ban and a zero ownership rate, but twice the US murder rate and eight times the murder rate of Germany, where guns are plentiful. Belarus totally banned handguns and got five times the murder rate of Poland, where they are allowed. Russia banned them and got a murder rate ten times that of Poland, plus a whole Youtube genre of traffic confrontations where everyone piles out with sledgehammers and baseball bats, in a country where they don't even play baseball.
As for the UK, one of their criminology studies said
No matter how one approaches the figures, one is forced to the rather startling conclusion that the use of firearms in crime was very much less - in England before 1920 - when there were no controls of any sort and when anyone, convicted criminal or lunatic, could buy any type of firearm without restriction.
Now that the UK has banned guns, the cops are starting to carry pistols to defend themselves against all the new gun-wielding criminals.