571.030. 1. A person commits the crime of unlawful use of weapons if he or she knowingly:
(1) Carries concealed upon or about his or her person a knife, a firearm, a blackjack or any other weapon readily capable of lethal use; or
so - the statute starts off by saying its illegal. There are a whole list of exemptions, but the important ones are:
3. Subdivisions (1), (5), (8), and (10) of subsection 1 of this section do not apply when the actor is transporting such weapons in a nonfunctioning state or in an unloaded state when ammunition is not readily accessible or when such weapons are not readily accessible. Subdivision (1) of subsection 1 of this section does not apply to any person twenty-one years of age or older or eighteen years of age or older and a member of the United States Armed Forces, or honorably discharged from the United States Armed Forces, transporting a concealable firearm in the passenger compartment of a motor vehicle, so long as such concealable firearm is otherwise lawfully possessed, nor when the actor is also in possession of an exposed firearm or projectile weapon for the lawful pursuit of game, or is in his or her dwelling unit or upon premises over which the actor has possession, authority or control, or is traveling in a continuous journey peaceably through this state.
and
4. Subdivisions (1), (8), and (10) of subsection 1 of this section shall not apply to any person who has a valid concealed carry permit issued pursuant to sections 571.101 to 571.121, a valid concealed carry endorsement issued before August 28, 2013, or a valid permit or endorsement to carry concealed firearms issued by another state or political subdivision of another state.
Bottom line: handgun concealed in vehicle OK with or without CCW, loaded or unloaded, if over 21. Long gun concealed in car OK with CCW, or if unloaded and ammo not accessible, or if not readily accessible, or if traveling in a continuous journey peaceably through this state. Long gun loaded concealed in car w/o CCW and journey non continuous = class D felony. Long gun NOT concealed is legal regardless.