Hi, a little update:
On Wednesday, I managed to play a game against my brother, using the boarding action rules from the Badab War book. Took some pics, although as always, I got caught up in the action too much to think of taking ENOUGH pics.
The scenario is set in the aftermath of the Siege of the Imperial Palace, after the Emperor slew Horus, and Imperial Forces are hard at work driving the traitors out of imperial territory. In the solar system, several pockets of resistance remain - one of these is the listening post/logistics base of Beta-Omicron on Rhea, orbiting Saturn. A strike team of Imperial Fists has been dispatched to purge the base of the traitors, who used it as a base to stage raids on the Jovian shipyards.
The loyalist forces comprised of a Chaplain on foot, a platoon (e.g. three squads) of tactical Marines split into six combat squads, a Contemptor Dreadnought and an Ironclad Dreadnought. The traitors (represented by my brother's Imperial Guard Galatean Regiment focused on Veteran Squads with a special-weapon-heavy loadout, a squad of penal legionnaires, a squad of Ogryns, one Lord Commissar and an Officer, as well as two plasma cannon-armed Sentinel walkers.
The battlefield was 4"x4", with the majority of the table as a built-up area (represented by some nice dungeon tiles). Outside of the BUA, the rules for Vacuum environment ("Cold Void") were in force, and we also used the possibility of catastrophic events, such as Wildfires and Decompression in the station. All troops were assumed to have sufficient equipment to fight in the void, but apart from the Dreadnoughts and Sentinels, no model had "Void-hardened" armour which provides extra protection under the rules. Basically, all attacks of strength 4 or more are made more deadly if made in a vacuum - this of course favours the Marines, who have S4 melee attacks AND boltguns, and makes the special weapons the Guardsmen have more valuable/mission critical.
This is the deployment stage. Half of each force is deployed (I managed to pass a roll that allowed my Marines to choose their deployment quarter, and chose to deploy close to the nearest airlocks); the rest is kept in reserve, which in my case were the three combat squads with missile launchers and one more squad with a close-range loadout. Imperial Fists are marked yellow, Traitors red, airlocks (counting as difficult terrain rather than blockades to be destroyed) are green, and the four objectives are blue (one plasma reactor, one communication node, and two Valkyrie gunships).
I was lucky enough to win the initiative roll and went first. My Contemptor breached the closest airlock, drawing line of sight of the plasma reactor and obliterating it with its assault cannon.
Other Marines followed suit, but some poor rolls meant I did not enter the station in force in the first turn. Related to that, the traitors repositioned themselves, but only got off a few desultory shots. One veteran squad with multiple meltaguns managed to get dangerously close to my Contemptor.
In round two, some reserves arrived - two of my combat squads, one with a missile launcher being dispatched to take out the Valkyrie parked outside the station. The squad of penal legionnaires, however, also arrived and made good headway to the Marines, charging through the cratered moonscape.
Inside the station, the Ironclad advanced inexorably and destroyed the communication node with a short-range melta blast.
Beyond the docking bay, however, things weren't looking as good - an Ogryn squad with attached Lord Commissar sprung from a side corridor (arriving from reserves) and charged the Marine combat squad and Chaplain, killing two Marines and wounding the Chaplain for only two wounds in return.
On a more positive note, the Contemptor swiftly rounded a corner, charged and dispatched a unit of Veterans wielding four meltaguns in melee - close call, that one, and only made possible due to the Contemptor being able to "Fleet" (i.e. move, run in the shooting phase, and charge subsequently). Groans ensued from my brother.
Outside, the penal legionaires managed to whittle down the Marine combat squad to three men, for only one loss in return - fortunately, I passed my leadership test, and hoped for reinforcements.
Round three saw the traitors reposition themselves to hold the docking bay.
The melee against the Ogryns continued, the Contemptor charging in to the rescue and taking down two of their number, the Chaplain and Lord Commissar being locked in a duel to the death, as the last of the Marines of combat squad Abel-One fell.
Timely, another combat squad of Marines arrived from reserves to charge the penal legionnaires. Under the combined onslaught of the two combat squads, they were cut down to the last man.
Round four saw the battle on the inside draw to a conclusion - the Contemptor and Chaplain managed to slay the last Ogryns and the Lord Commissar.
Outside, combat squads Abel-Two and Caspar-Two, having previously eliminated the penal legionaires, trained their missile launchers on the Valkyrie and obliterated it with well-placed missile shots.
With three objectives being destroyed, the traitors attempted a last-ditch firefight, directing a hail of plasma fire at the Contemptor, only to see it bounce off its atomantic force fields. Their leadership gone, the traitors surrendered to the mercy of the loyalists (and we all know how well that will end).
A fun game, although a number of lessons had to be learned.
First, the mission falls into the "Forgeworld LOVES Space Marines" category - high strength and good saves make them very effective, although to be fair, from the fluff, they should be. Still, if we want to play more boarding actions in the future (and I am sure we will, as it was quite exciting, fast and bloody), if the defenders are Imperial Guard, one needs to set up the table with more intervening terrain, and place objectives in a way that makes them harder to reach. Also, next time we will be using stratagems - especially in a sabotage mission, delaying the attackers will be critical.
Second, the Contemptor is brutal. It costs a lot of points (almost 200), but it is painfully fast and nimble, as well as awfully well-protected by its high armour and shields. I probably will not field it anymore unless I have told my opponent in advance (I had mentioned it to my brother before, but the number of AT weapons he brought were not up to the task and quickly reduced by the Contemptor's agility). It's awesome to play from a Marine player's point of view, and even better in the BUA than the Ironclad, but even I think it is dangerously close to being overpowered.
Still, fun was had by all, although it turned into frustration for the traitors.
I strongly recommend giving rules like this a try - that said, the Badab War book is quite pricey, and a similar set of rules was available a few years back from Games Workshop themselves (in one of the Chapter Approved books), and the free Badab War PDF put out by the Fly Lords of Terra and Bell of Lost Souls (which came out a couple of years ago, mid-2000s, IIRC) has another nice variant which should play nicely. In particular, if the armies are closely matched in capability, e.g. Marines vs. Traitor Marines, or Marines vs. Eldar, it should make for an exciting departure from the usual slugfests. That said, the next game will probably be a big tank battle, Marines vs. Guard, and I am looking forward to that one, as well, although I need to figure out how to bring in some ack-ack to deal with his air cavalry.