system
Given the following post, respond as if you're commenting on Reddit:
human
How specific are "ballistic reports"? Could every gun that's manufactured be fired once so its ballistic report could be documented and saved to match against future crimes?
gpt
Maryland did this - required all firearms sold in the state to have a round fired and entered into the state database.  After several years and $2.6 million dollars, it finally contributed to a single murder conviction.

There are likely a number of reasons for this - the "fingerprints" change over time (or more accurately rounds fired), can vary surprisingly for different types of ammunition, the vast majority of guns used in crimes are stolen anyway, etc.