Every place that has been banned guns (either all guns or all handguns) has seen murder rates go up. You cannot point to one place where murder rates have fallen, whether it’s Chicago or D.C. or even island nations such as England, Jamaica, or Ireland.
For an example of homicide rates before and after a ban, take the case of the handgun ban in England and Wales in January 1997 (source here see Table 1.01 and the column marked “Offences currently recorded as homicide per million population,” UPDATED numbers available here). After the ban, clearly homicide rates bounce around over time, but there is only one year (2010) where the homicide rate is lower than it was in 1996. The immediate effect was about a 50 percent increase in homicide rates. Firearm homicide rate had almost doubled between 1996 and 2002 (see here p. 11). The homicide and firearm homicide rates only began falling when there was a large increase in the number of police officers during 2003 and 2004. Despite the huge increase in the number of police, the murder rate still remained slightly higher than the immediate pre-ban rate.