I like you. I'm a Metroid fan myself, sir.
I've played all the games except for Metroid II for gameboy. You don't need to find my scans, I have most of the basic knowledge memorised from my three or four play throughs of the prime trilogy.
That said, I'm reasonably certain a bolter would be equivelant to missile spam, for example. Bolters are incredibly powerful weapons, not wholly ineffective against 40K tanks. (though not particularly effective, either.)
Comparing dstructive feats, the SA-X's super missile can damage and partially collapse a hallway in a space station made of an unidentified metal. We don't have a feat for her normal missiles, unfortunately.
A bolter shell is designed to peirce armoured targets, and is tipped with diamantine. It then explodes with enough force to rip apart a man in ceramite power armour.
I think it'd work fine on your typical pirate's armour, some exceptions exist, but a named space marine such as Tarkus, Avitus, Cyrus, or Thaddeus is going to be carrying more than just a bolter. Thaddeus is probably the second most dangerous to a pirate, next to the force commander himself, due to his melee orientation and his jump pack.
But like I said, this is all speculation until we know what the thread is actually about.
It could even be v.s. a starcraft marine.
Hyper mode would be an interesting twist, to say the least, if this is a 40K marine.