Mo. Rev. Stat. § 571.037: Open display of firearm permitted, when.

Any person who has a valid concealed carry endorsement issued prior to August 28, 2013, or a valid concealed carry permit, and who is lawfully carrying a firearm in a concealed manner, may briefly and openly display the firearm to the ordinary sight of another person, unless the firearm is intentionally displayed in an angry or threatening manner, not in necessary self defense.