If you have a brass or carbon fiber rod, then a rod is a good option. Definitely use a brush.
I highly doubt it would destroy your barrel - but better safe than sorry.
Hunting is a loophole in the 2nd Amendment to the Bill of Rights.
There is no privilege to keep and bear arms.
Arms are for killing people. All other uses of an arm are illegitimate uses.
Know your rights. When stopped by police and not doing anything wrong, tell them you don't consent to searches. They are allowed to lie to you, but you're not allowed to lie to them. Just say nothing.