Is a blackpowder gun consideres a firearm, I would say YES. Following is the defination from Black"s Law Dictionary;
FIREARM: An instrument used in the propulsion of shot, shell, or bullets by the action of gunpowder exploded within it. A weapon which acts by force of gunpowder. People v. Simons, 124 Misc. 28, 207 N.Y.S. 56.57. This word comprises all sorts of guns, fowling pieces, blunderbusses, pistols, etc.; Harris v. Cameron, 81 Wis. 239, 51 N.W. 437, 29 Am.St.Rep 891; Atwood v. State, 53 Ala. 509; Whitney Arms Co. v. Barlow, 38 NY Super. Ct. 563; fountain pen primarily intended for discharge of tear gas, People v. Anderson, 236 App.Div. 586, 260 N>Y>S> 329; but not an Air pistol. People v. Schmidt, 221 App.Div. 77,222 N.Y.S. 647.650.
This is a rather loose discribtion, but Black"s is generally the book used by most courts to define the law. As a layman, I still read this to include any instrument capable of discharging shot, or bullet to be a firearm, and think that most courts would agree with this.
As for letting a policeman know that I am carrying, under the Texas law, if you are in a vehilce you must not only provide the officer your driver's license and proof of insurance when stopped, you also must provide you concealed carry permit. The permit is linked to the individuals driver's license,(both carry the same number). Failure to do so can relsult in a felony charge and/or or you concealled carry permit being pulled.
It is my personal opinion than any time anyone is stopped by an LEO while carrying, they should, first thing, inform the LEO that they are carryiing. This is a safety issue, and may keep someone from being shot, or otherwise abused, because the cop seen the gun and went into a panic. Even in far West Texas we have those cops from the big city that do not have experience with guns, and still harbor that big city mentality reguarding them. Better safe, than sorry!
As for the effectiveness of the black powder guns, they will do the job as long as you keep your powder dry........If you have ever fired a black powder, you know it takes a "spell" for the smoke to clear after you shoot, so you have to make the first one count. The use of firearms in the old west as displayed in the movies is far from accurate. Most people killed in the old west were eithe killed at close range, or back shot for a fairly close distance. The practice of calling someone out, meeting in the street at 40-50 was largely unheard of.
If a black powder was all that was available, then I would use it, but I hope I never get to the point I have to relie on one................