Probably with about the same alleged certainty as fingerprints. :-(
In the end a determination is made by fallible humans.
My original point was responding to the claim that a bullet can be identified as coming from a specific type or model of gun, without having the gun to compare it to.
The FBI report is about weapons in evidence . That is weapons recovered as evidence from the crime scene .
The FBI is stating that they can link one of the rifles recovered at the scene to the bullets that killed the Border Patrol agent and BATFE is claiming that the FBI report says something entirely different.
The MSM know that the BATFE is lying to them to their face & does not like it.