Radley Balko has a great overview on the fundamental flaws with ballistics forensics[1]. The tl;dr is that the core claim of ballistics forensic analysis, that it is possible to reliably differentiate between two models of the same gun using just casings and shells fired from those guns, has never been proven to be valid.
[1]: https://radleybalko.substack.com/p/devil-in-the-grooves-the-...