Also one imperial starship was described as "having no void shields but a meters thick solid adamantium hull. (No it wasn't named the "Wolverine".)

I like to think that all ships have a meter thick hull, as otherwise I don't see how they could at least partially withstand stuff like lance attacks and macrocannons. However, at the same time, each ship will also have weak spots - you can't have an airlock that is as thick as a meter, and whilst the weapon bay doors may be armoured they will have to open in order to allow firing (which reminds me of how you'd attack one of those airships in Crimson Skies).

These are the areas I'd target during a boarding attempt. And coincidentally, this is exactly what happened in that BFG short story that Andy Chambers had written, too (-> bunch of boarding torpedoes slamming right into the weapon bay).

I mean meters as in dozens of meters not a few. And it's adamantium. Basically the ship took a lance salvo (wich normaly blows straight trough anything smaller than a battleship) and barely felt it. It was built in a time before voidshields and the imperium later never fitted it with shield generators...Because it didn't need them.

Speaking of weapon bay doors:

There's a book (I think it's a dan Abnett novel) in wich a chaos flyer flies trough the ships hangar into the ammo conveiance tunnels before "catastrophically running out of space" near the ammo storage. Scratch one imperial vessel.

I like Crimson Skies, some of those things were as aerodynamic as the stuff the imperium produces.

I like Crimson Skies, some of those things were as aerodynamic as the stuff the imperium produces.

Indeed. Switch the propeller for a jet turbine and this becomes an Imperial Navy interceptor.

This one on the other hand looks almost orky.

Ahh, good times ... dammit, Microsoft, why do you have to hog all those good licenses! Poor Mr. Weisman comes up with one awesome game after another, only to see the settings rot in MS' backyard.

There was also a TT version and an RPG if i'm not mistaken.

No RPG I think, but a tabletop from Wizkids, and a bunch of novels.

But I want a sequel of the PC game! It was a great dieselpunk setting (actually reminded me a little of Disney's TaleSpin cartoon), and the gameplay was rock-solid to boot.

But .. back to Astartes boarding now, we wouldn't want to derail the thread entirely.

I don't think it's so much of breaching the outer hull as it is breaching something valuable in the inner workings. LIke that chlorine gas pipe, or plasma battery coolant, or power regulator. It's like firing a gun inside a submarine - "Somethings in here don't react well to bullets."

Or the control interfaces.

The outer hull is not going to get breached by accident. Things that are structural aren't going to be harmed either. What's at issue is the softer parts - not every wall is going to be of structural strength, and not every hatch is going to be a blast door, but most of the time they're also going to be reasonably sturdy, just not rated to resist a sustained and deliberate attack. Access panels will be fairly weak, but if you accidentally take one or two out, most of the time you're only going to cause local disruptions, unless you're in a primary systems support access conduit, which will tend to lie alongside/wrapped around major structural elements, and generally aren't going to be high priority targets, and sure, they'll need to get cleared, eventually, but the plasma reactors are way more important, for example.

The real problems are when you're attempting to take things like the engineering and command and control sections, or flight/vehicle support areas and armory/munition storage areas. You want to be careful about areas where collateral damage (or misses) can cause secondary explosions or take out vital system controls, or the systems themselves.

So, you'd want to switch to lighter weapons for those areas ... but you can only carry so much at a time, which means you have a couple guys with heavy weapons/breaching equipment and everybody else with the lighter stuff to start with. Alternatively, roll with medium to heavier weapons and switch to melee when you're worried about collateral damage/misses messing up something important or sensitive. That's basically what Assault Marines do.

Plus, blast effects get magnified a fair amount in the relatively confined spaces aboard ships.

One example of why shipboard firefights can be problemmatic is in the beginning of Ciaphas Cain The Last Ditch, IIRC - they blew the dickens out of the bridge as collateral. Admittedly, that wasn't exactly a 'normal' situation, but it serves to illustrate why heavy weapons are often frowned upon.