I saw MythBusters showing the bedliner blast as it protects blasts from an explosion then I saw one video of it being bullet proof, but I guess I am a prove it kind of guy. Will a well painted car door with bedliner be bullet proof? OR could a bedliner painted front door stop a bullet?
As a starting point of reference, the spall/fragmentation coatings on some steel armor plates are supposedly very similar to bed liner coating. I think they are usually 1/4” thick or so. The coating doesn’t slow the bullets down at all. It just catches the fragments after the bullet expends most of its energy against the thick hardened steel. I would suspect you would need many inches of liner to slow down even a low velocity pistol bullet enough for the thin car door steel to stop it. that’s a lot of spraying!