There are provisions for minors(under 18)to possess and carry a handgun under certain limited conditions -- very limited. At 18, you could not carry a concealed handgun, or have a loaded handgun in your vehicle, but as I read the statutes, nothing prohibits open carry.
I have discussed this with LEOs in the past, and those I spoke with were not familiar enough with the statutes to realize that an 18 year old can OC legally. If you choose to do so, I would suggest you carry a copy of the entire 9.41 statute, as otherwise you may have some sticky situations if you are stopped by LEO.
Perhaps this is another topic that warrants a training bulletin(s) to clarify for LEOs.
I am not a lawyer, and this is not legal advice.