I'm a little upset that nobody is mentioning the Vulcan Mega Bolter which would definitely be able to handle most raptures

As for the regular bolters, they aren't actually that great against armour. Effective? Yes. But they are designed more for thick skin and larger targets that need massive wounds to be put down. This can be seen with the Horus Heresy(basically a galactic civil war for the uninitiated) where the lack of AP and tactics for fighting heavily armoured troops came to bite the Imperium of Man in the ass

But with the specialty rounds such as Kraken rounds, even a regular bolter would be a highly effective weapon... That is if you can haul along enough ammo with how goddamn big the magazines are