ELI5.How forensic analysts match a bullet to a gun?

Question

How do ballistics/forensic analysts match a bullet from a victim or found on the scene to the EXACT gun that fired it?? I mean a 9mm bullet can be loaded into any 9mm firearm right? So how do they know exactly which gun that fired it? How do they match it?

In: Engineering

Answer 1

So, if you replace the barrel after using it (and maybe the firing pin), will that be enough to throw off the analysis?