I don't think its necessary.
But thousands swear by it.
There's been a couple of barrel makers that think it's a good idea. That's 'cause lots of people clean barrel wrong and wear them out too fast. So they'll be able to sell more barrels that way.
Bore snake? Personally, I think they're one of the best jokes or myths in the firearms industry since someone claimed rimless bottleneck cartridges lay in the bottom of the chamber when fired.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master