How bulletproof is fiberglass paneling, anyways?
Well Taofledermaus has some fiberglass paneling to try against bullets.
Watch as fiberglass paneling is shot with both 9mm and 12 gauge slugs.
How well do these fiberglass panels do against actual bullets? Well, a fiberglass panel is mounted to a dummy. It is targeted by both a 9mm pistol and a 9mm rifle. It stopped those bullets cold. The 12 gauge shotgun slug blew a big hole in the panel. That slug is certainly a higher power than the panel was meant to ever handle.
In short, the fiberglass panels did what they were expected to do and more. They just might find a place in the construction of your home or office.