A ccw permit has nothing to do with open carry in Missouri. Open carry is legal, permit or not, by state law. The only problem is that open carry is not covered under preemption statues in Missouri. Many cities (mostly urban and suburban, but some rural) have laws against open carry. In unincorporated areas, open carry would be legal in most every county. The only way to know for sure about a city or town is to ask, although some websites can give some guidance.
See:
http://www.natesit.com/oc/mooc.htm
http://www.natesit.com/images/kcocmap.jpg
Even if it is legal, if you are in town and not out in the field, you may attract attention you don't want. This is especially true if no one else has open carried in town for many years. In one city in the St. Louis area an individual practicing legal open carry caused such a stink that a city ordinance against the practice was quickly instituted in response.