My group usually implements the house rule of "if an attack causes more damage than your armour reduces it does a minimum of 1 damage, regardless of toughness reduction."

This works pretty well in most games but some of us are doubting it's implementation in Black Crusade. Frankly it makes us feel a bit too vulnerable.

What do you guys think?

Are we talking armour or armour+toughness here?

For example:

I get hit in the chest for 17 damage. My armour reduces that by 10 for a total of 7. My toughness bonus is 8 so the damage is reduced to -1. 

But since the attack did more than 10 damage, it got through my armour and therefore does a minimum of 1 damage, regardless of how much my toughness reduces it.

Zealous Hatred more or less does this, but only on a roll of a 10 on one of the damage dice.  The rule you are proposing makes characters more able to be plinked to death; suddenly high RoF weapons like, say, an autogun can do a not-insignificant amount of damage if they catch someone with their pants down.

I don't like it and would not want it in a game I was in. It's more or less the ZH thing but it can happen with more or less every attack unless you're wearing terminator armour. Might as well do a houserule called "any attack does atleast 1 damage".

There's a legacy ability that allows 1d5-2 when a weapon otherwise fails to cause damage. That's a special gift to a dedicated weapon.

Under your rule, an autogun, or that stubber with Storm would become the ideal Tank-Hunter weapons. A guaranteed 10 is greatly superior to the vast  majority of available weapons; especially given the autogun's availability.

In fact, if you get recoil gloves and dual-wield…. at that point you should be outdoing just about any weapon that isn't already vehicle-mounted [and a decent amount that were] in average output against big fat targets like a Leman Russ' front armor or Land Raider.

It would be more reasonable for you to lower unnatural toughness a little, or grant +2 of it to squishies and upgrade weapons by 2 damage to compensate. Not that doing so is a particularly good way of dealing with the output problem of the weakest weapons.

Thanks for the replies!

I brought your points to my GM and after a discussion we rescinded the rule.