It seems a bit odd that ammo rolls are avoided for Krak and Melta Bombs by virtue of not having to make a to-hit roll. In fact, you can never run out of Melta Bombs or have one go off in your hand, since their only use is as demolition charges.
The more I think about this, the more it seems that demolition using grenades should be part of the preceding shooting section. Treating it as shooting will also mean that the Fighter cannot run, charge, shoot another weapon or be engaged in HtH while using grenades for demolition.
This change will mean that the demolition charge hit will now happen in the shooting phase rather than the HtH phase. But I from what I can see, this doesn't really matter.
The more I think about this, the more it seems that demolition using grenades should be part of the preceding shooting section. Treating it as shooting will also mean that the Fighter cannot run, charge, shoot another weapon or be engaged in HtH while using grenades for demolition.
A structure can be shot at just like an enemy fighter. You must therefore roll to hit and score wounds as normal. Some structures will be easier to hit than fighters because they are large targets (+1 to hit). A Fighter in base contact with a structure can instead use Krak grenades or Melta Bombs as demolition charges. This is treated like shooting in all respects (no running or charging etc.), except the target is hit automatically. Make a roll to hit anyway to see if the they run out of ammo or the bomb explodes prematurely in the Fighter's hand.
A fighter can use Krak grenades or Melta bombs as demolition charges. The device can be placed upon a structure in base contact of the fighter during his hand-to-hand phase as long as he didn't run or charge. This is considered to be shooting although no roll is required to hit. The bomb is fastened to the structure by means of its magnetic casing, it explodes, and the target is hit automatically.
This change will mean that the demolition charge hit will now happen in the shooting phase rather than the HtH phase. But I from what I can see, this doesn't really matter.