Don't look back, don't hesitate, shoot it!
Don't worry about shooting real black powder, it's actually much easier to clean up than you think. The real stuff is water soluble, so it dissolves easily. I clean my Sharps with nothing more than soapy water. When I clean my rifle I run wet patches through the barrel until they come out clean, then a brush to knock loose any residue, then more wet patches until they're clean again. Then I push dry patches through until the bore is bone dry, and then I oil it. That regimen may be overkill, but I actually enjoy cleaning guns
It sounds like a pain, but in reality it takes less time to clean a black powder cartridge rifle than it does to get the copper out of a modern rifle bore. You're talking maybe 5 minutes of work.
This rifle was made for black powder. Generally speaking, you can't fit enough BP into a cartridge to harm a gun. If you shoot the holy black in your rifle you know it will always be safe. Just clean it well and you have nothing to fear.
