Implied in your original question is can a 17 year old IN resident leagally carry a C&B pistol, since some may consider it a curio or relic, not a real pistol. The answer is no you can't, and the law does not have a special category for relics.
Your sidebar info shows you are 17 years old and a resident of IN. It is illegal in IN for a 17 year old to carry a pistol, other than under certain conditions such as hunting or a shooting range.
Loaded/unloaded, concealed/open, modern/antique, trained/untrained, skilled marksman/unskilled makes no difference, the IN law is clear: you must be 18 years of age or older. The point is not if an 1851 Colt is an adequate defense firearm, the point is you are considering violating IN law. And you know this as you state you need to wait to be 18 to get a CCW permit.
If you choose to knowingly violate IN law and carry when underage, and you are not arrested, and no one knows except you that you are illegally carrying a firearm, then at best you only have a character flaw which I hope does not re-appear on other matters.
No one can estimate the probability you will be caught violating IN law and perhaps you think it is very low. But if caught, the consequences are well known and severe. At 17, you may have trouble grasping the severity of these consequences.
But as I and others have already stated, if convicted of of a felony for violating IN carry law, this will forever close many of your life's options, including joining the military, law enforcement, many civilian jobs, and likely impact your ability to borrow at favorable rates.
If you use lethal force in a life-threatening situation, and a Grand Jury does not indict you, or a trial acquits you, you will still be convicted of violating IN law for carrying underage.