There is a new product out called "Evaporust" which you can find at O'reilly's auto parts stores, among others, that will not only remove rust, but slightly reverses the process so that some metal remains. I would pour a tblsp of this down the bore, give it a good shake, and let it soak in a plugged breech for a day to remove all the rust. Pour it out and rinse the bore with soap and water. Wipe dry, and then oil LIGHTLY with a good grade of gun oil.
Before actually shooting the gun, flush that oil out of the barrel using alcohol. Run a drying patch down to remove any remaining alcohol after you pour it out. Then load and fire.
The T/C guns are well made. But, they are made to be shot using the patched round ball. Try .530" diameter balls, with .018" thick patches. Lube with spit, water, Hoppes Black Solve and lube, Wonderlube, etc. Your choice. They work, but every gun has its preference.
I recommend using Black powder, and start with a load of 50 grains of FFg powder. Work up from there in 5 grain increments. Some guns will like the .535" ball diameter, and some will like FFFg powder better.
Understand that you have a smaller diameter Powder Chamber at the breech, which has a small hole in the center of the chamber, that leads to a flash channel. The channel then goes to the side of the barrel and under the Nipple. You need a nipple wrench to remove the nipple for cleaning, and pipe cleaners to get down into that flash channel. A .36 caliber( .38 spl or 9mm) Jag will fit down into that powder chamber to help you clean and DRY IT.
Because the diameter of that channel is small, some guns( not all) have been known to be fussy about what size powder granules they will let flow through them. Pyrodex comes in 3 grades, RS, P, and "Select". You don't indicate which you have to use. While I would prefer the lower pressure, slightly slower burning RS for this gun, you probably will need to use the smaller granule sized, Pyrodex P powder to insure that the powder flows properly through the barrel, powder chamber, and flash channel.
Keep the powder charges light- if you are comparing the Pyrodex load, BY VOLUME, to the loads used with Black Powder. Increase the powder charges slowly as you check for any leaks of gas. Reduce the volume load of Pyrodex by the company recommended 25% of the volume designated using Black powder.( An adjustable powder measure comes in very handy for this kind of testing.) Pyrodex is less dense than Black Powder. While we discuss Black Powder loads in reference to Grains, which is a measure of weight, Black Powder, as well as the substitute powder such as Pyrodex, are measured by Volume, and not on a powder scale that measures grains as weight. ( Smokeless powder cartridge reloaders are used to this equipment, and terminology.)
For instance, 50 grains of BP is comparable to 40 grains of Pyrodex.( The difference between the two charges by volume are 10 grains, which happens to be 25% of the 40 gr. volume of pyrodex use to equal that 50 grain charge of BP.) 60 grains of BP is comparable to 48 grains of Pyrodex. 70 grains of BP is comparable to 56 grains of Pyrodex.
Check the website for Hodgdon to get more information on how to use Pyrodex.
Without actually visually inspecting that rifle to see how much damage has been done, NO ONE here can do much more than guess on whether the gun is still safe to shoot, or not.
I recommend that you take the gun to a Black Powder Gunsmith, and have him check the condition of the barrel, before firing it with anything. Its simply not the risk of injuring you, or people standing around you to fire the gun without knowing its still safe to shoot.
:surrender: :thumbsup: :thumbsup: