If anyone here watches RWBY, Roose's gun is exactly like that.
If nobody here watches RWBY, Roose is a ghost, and he is attached to his gun spiritually. This means it is much more resistant to things like ballistic damage, erosion and oxidation. With that much strength in his gun, he can actually fill the barrel with TNT and shoot himself into the air with it.

Since he's a ghost, he can also take a cannonball and hold it against the flared end of his gun and fire it. His arm has a much smaller chance of getting ripped off. He can still get injured, but since his spirit acts partially as a source of Mana, he can use magic to heal the wounds instantaneously.