And as someone who has shot firearms all my life, I am telling you that CSI is BULLSH*T if they portray "bullet-matching" techniques as applicable to muzzle-loading arms. It is hard enough to get a bullet fragment from a rifle to match the barrel; usually the only recourse is neutron activation or other mass spectrographic technique.
Furthermore: I doubt most people on FR even realize that black powder arms ARE NOT FIREARMS, at least by the FedGov's definition.
See post 114
I believe it is possible.
Firing a minie ball through a muzzle-loader would presumably leave rifling marks in the ball that could be used in ballistic forensics. Not commonly done, but not impossible.