"...and requiring those who do to carry third-party insurance in case an accidental discharge ends up injuring someone is an absolute minimum."
The thing here is that accidental discharges don't happen if you properly maintain your weapons and ammunition, and if you handle them properly.
As an example, I wouldn't store any weapons with a round chambered, wouldn't store weapons loaded, and wouldn't use any rifle or pistol rounds in an apartment for self-defense because of over-penetration concerns. The case where you have an accidental discharge and it hurts someone or something is entirely preventable using common sense, and so I don't believe that we should require insurance against what is honestly improper and unsafe tool usage--that burden should rest on the person who caused the accident.
As over 90% of road traffic accidents are the result of human error, I strongly disagree with your conclusion -- otherwise we wouldn't need third-party insurance for cars, either.
(On the other hand, if you're as sensible as you say, I have three words for you: no claims discount.)
Quick searching is not instructive as to pricing, but I guess some homeowners policies cover gun accidents, and such insurance is not particularly expensive.
Indeed, and you can tell from the costs what the insurance companies think are the serious risks (hint, not liability).
I'll just mention ratios, that I'm a USAA customer who's father was in the military (eyesight kept me out, but they have a special category for us because we're better risks), that I don't have very many guns, have a monitored alarm, and no longer get the no claims discount (http://en.wikipedia.org/wiki/2011_Joplin_tornado).
All that said, I pay 4 times as much for the extra protection needed to cover loss of my guns as I do for the liability insurance that's an enumerated part of my renter's policy, and the single instance liability they're on the hook for is 35 times greater than a total loss of my listed guns and scopes.
The thing here is that accidental discharges don't happen if you properly maintain your weapons and ammunition, and if you handle them properly.
As an example, I wouldn't store any weapons with a round chambered, wouldn't store weapons loaded, and wouldn't use any rifle or pistol rounds in an apartment for self-defense because of over-penetration concerns. The case where you have an accidental discharge and it hurts someone or something is entirely preventable using common sense, and so I don't believe that we should require insurance against what is honestly improper and unsafe tool usage--that burden should rest on the person who caused the accident.