How does penetration work?

[doubleskulls]

I just shot an accelerated rifle at a mentarch with 25 armour, and only managed to do 2 points of damage. 

I would expect that 40 damage base, worst roll is 50% = 20. So the armour absorbs it all, however accelerated rifles do 5 points of penetration, so I'd expect at least 5 points even with a minimum roll. Is this a bug or is the logic different to what I expected? 

[Chris]

15 minutes ago, doubleskulls said:

I just shot an accelerated rifle at a mentarch with 25 armour, and only managed to do 2 points of damage. 

I would expect that 40 damage base, worst roll is 50% = 20. So the armour absorbs it all, however accelerated rifles do 5 points of penetration, so I'd expect at least 5 points even with a minimum roll. Is this a bug or is the logic different to what I expected? 

The logic is slightly different. Penetration basically just reduces Armour prior to the damage calculation, so the Mentarch effectively has 20 Armour - and then the lowest roll would be 20 damage, which should cause no damage.

I suspect the 2 damage is either because someone shot the Mentarch first and took it down to 23 Armour, or there's a minor issue with the ordering of armour destruction and that is being applied prior to the damage calculation.

[doubleskulls]

Thanks for the explanation, that makes perfect sense with what I'm seeing then. My, mistaken, assumption, was that penetration by-passed armour, rather than just negated a proportion of it. Funnily enough that doesn't make any difference to the relative benefits of accelerated vs basic lasers. For rifles accelerated are marginally better right up to 44 points of armour.