[iconoclast]

"What would the downside be?"

Respectfully, I'm still asking.

IMO your only pertinent point is your #2, and the second amendment has long since and way worse been infringed than by what this firing pin print thing would do.

[two23]

Again---fingerprinting firing pins and bores is just one way to create a national data base which can ultimatly lead to confiscation.
Look, people can modify weapons, there are millions on the street already---criminals do NOT play by the rules, so once again...innocent gun owning Americans take the heat for the bottom feeders who don't play by the rules.

[iconoclast]

"What would the downside be?"

Mea culpa

I'm backing off, folks.

After my second cup of coffee, the record keeping puts me off, too.