If a unit of 10 VTB bases (Let's say scarabs) get's hit by a instant kill template, and then recieves 5 wounds, those wounds are doubled to 10, and then you remove 10 bases.
no, as the wounds have been inflicted before the doubling as you can see below.
1. Vtb rule states that wounds done to a unit, not to models, are doubled. (Pg. 76 BGB)
2. Multiple wound models MUST be removed WHENEVER possible. (Pg. 27 BGB)
3. When a model takes a wound from a weapon whose strength is double it's toughness it is removed IMMEDIATELY. (Pg. 27 BGB inside the box).
4. Wounds may not be allocated to AVOID removing models (pg. 27 BGB)
So the above scenario would look like this:
1. the unit takes wounds from a template (whether from failed cover saves, or pierced armor doesn't matter).
2. The wounds are doubled.
3. One wound is assigned to each model killing it instantly, till all wounds are allocated, or all models have been removed.
and you're totally skipping over the whole issue about removing casualties and assigning wounds, aren't you.
5 wounds means five doubly dead scarabs.
You've got your 2 and 3 mixed up, try again.
Find majority toughness
Roll to wound vs majority toughness (or lowest in case of a tie)
Remove any models that are wounded and don't get a save
Apply 1 wound to each model based on majority save, starting with majority, and then proceeding as you wish without applying a second wound unitl every model has a first.
Wrap around, starting with majority save again.
Note: torrent of fire allows the shooter to nominate ONE model to make A save. The owner decides against which weapon.
Remove casualties from the appropriate saves, all extra wounds are lost
so, if I have 5 shots, all wound vs 2 termies and a master in powerarmour, 2 hits go to termies, 1 to master, 2 more to termies. shooter can say the termi with the assault cannon must take a save, so I roll his save seperately. then roll the termies, and the master. If I fail all four termie saves, they in no way spill over to the master, as he only has one wound to save against.
In the case of three different armours, it goes like.
Tactical squad (4 marines) with master in termi armour and apoth with 4++ gets hit with 11 shots. first four go to tact marines, next one goes to either master or apoth, next after that goes to the other, then start over, 4 more wounds to the tact squad, and one more wound to either master or apoth. 8 saves for the tact squad, 1 or two for the master, 2 or 1 for apoth. if the tact sqaud fails all 8, those wounds don't spill to any one else.
Same goes for your scarabs
5 hits vs 10 bases. one wound applied to each, which will instand death the 5 bases. Those wounds are then doubled, as they have been applied, as per Vtb.