Making guns more difficult to obtain legally does nothing to make them more difficult to obtain illegally, it only makes it more difficult for a private citizen to protect themselves. There is no evidence that there would be an arms race between ordinary citizens and criminals, this only happens between countries. The vast majority of criminals are merely opportunists and are not part of an organized group (with the exception of gangs), so it is unlikely there would be an arms race. Gangs are a different matter and they should be dealt with by the military like we are doing in Afghanistan and Iraq, the police have neither the weapons nor the training to go against most gangs. That is a whole other can of worms and gang members should be just shot on site.