Investigate Armed Citizens Legal Defense Network. It's run by Marty Hayes and his wife. I just talked to Marty at the NRA show. When a member has an incident and calls their phone number, that phone is in Marty's possession 24/7. Marty has people on speed dial that can help, including Massad Ayoob and a lot of other expert witnesses. Tom Gresham of Gun Talk was an initial investor.
Most importantly, the Network has a million dollars cash ready to go to help members. I've been a member four years now.
Couple things I'd mention, maybe some of FR's attorneys can clarify these things, I'm not.
Check with the company to see what you're purchasing, most do cover civil damages. As do some umbrella liability policys. Others specifically exclude firearms. Ask your agent and read the policy for an exclusion.
Also, while some may provide some funds up front toward attorneys fees and bail, it's insurance, largely paid at the conclusion of the case. It's your expense till then. That's what appeals to me about the Legal Defense rather than insurance concept, if I read their website correctly.
Also, if you're found guilty, insurance doesn't generally cover you if you were acting illegally. Something relatively simple, like illegal discharge in defense of your life, you might be OK but ask your attorney and the insurer if you might be depending on it.