But even then, what we can make an educated guess about is that while the amount of guns does not influence crime rate, the crimes that do happen in places where there are more guns would tend to be more brutal and in fact, the statistics support that.
http://en.wikipedia.org/wiki/United_States_cities_by_crime_rateCheck the crime rates of NYC versus the cities in Texas that have a similar crime rate (most have a higher rate). The rates of murders in the Texas cities versus NYC are 3 to 5 times higher.
And since you mentioned Chicago, Chicago has a lower murder rate than almost all large Texas cities. So, yes, other factors dictate whether someone commits a crime in general, but when they have guns, people are murdered at far higher rates.