Standard attack + Short Range = +20 or +10 (Ordinary ordinaries)

By Utherix, in Only War Rules Questions

Table 8-5: Combat Difficulty Summary states that Standard Attack and Short range are ordinary tests, so fulfilling two can't just become more ordinary, could it? An ordinary attack is an ordinary attack?

Or do two ordinaries make an extraordinary (Routine) +20 to BS?

The short answer is yes.

The longer answer is yes, because all modifiers are combined to determine the final Modifier to Attribute.

You use the base action as the starting point for determining the starting Difficulty and apply modifiers until done. In this case the Base Action is an Standard Attack Action (Single-Shot) (Ordinary +10) the only modifier it has is Short Range (Ordinary +10) which as being a positive modifier in a divisible of 10 (bonuses/penalties less than ten are not named, as you may have noticed), this improves the Difficulty by one step to (Routine +20).

Now if you had been making a Base Action of Semi-Automatic Burst(Challenging +0) at Short Range (Ordinary +10) then your modifier to Ballistic Skill would be (Ordinary +10), since you start with a 0 and have a positive bonus it improves the difficulty by one. (0+10=10).

And if you had done the Full-Auto Burst Base Action (Difficult -10) at Short Range (Ordinary +10) the your modifier to Ballistic Skill would be (Challenging +0), since you start with a negative (-10) and counter it with a positive (+10) for net value of 0.

For any additional modification you have; equipment, talents, comrades, etc. just move the modifier up or down the track. Every +10 moves it up (to the positive modifier) while every -10 moves it down (to the negative modifier). So if your total positive modifiers are +40 (Simple) and your total negative modifiers are -20 (Hard) then your final modifier to Characteristic is +20 (Routine).

Finally, just adding this bit, if your total modifiers (positive or negative) exceed +/- 60 (Trivial/Hellish) then they cap off and go no higher. However your bonuses or penalties before the final modifier CAN exceed this limit, but only serve to eliminate bonuses and penalties.

Example: By a stroke of good fortune you manage to wrack up a total of +80 in bonuses, normally you would only get the +60 (Trivial) bonus to Characteristic and the extra 20 would be lost. But, in this case, your character is shooting through the fog (Hard -20) and the extra 20 points goes to eliminating the penalty (20-20=0) instead of being wasted and you still get the smashing +60 bonus.

The flip side is also true, and you should definitely reconsider performing such an action that sunk you so far down that Hell looks nice.

Magus Black is almost entirely correct. I want to point out, however, that there can indeed be changes to Combat Actions that are not necessarily divisible by 10. There are equipment/craftsmanship that gives you +5, for example.

But yes, the Combat Difficulties list is really just a list of applicable modifiers sorted into brackets of 10. Apply all that may apply, to a maximum of +/- 60, roll.