Bitter Fury + Fury of Olympia: how many shots?

[Xenith]

As per the title, say. A tactical marine in rapid fire range, with the hammer of Olympia rite to gain bitter Fury (+1 shot) has the bitter Fury advanced reaction applied (weapons maken twice the normal number is attacks)

 

In a rush we said normally they would get 3 shots, which becomes 6, but in the cold light if day, I'm thinking it should be double the base shots first, so rapid fire for 2 attacks, doubled to 4, then add 1 for five. 

 

Rapid fire simply says makes 2 attacks, not 1 additional attack, so base attacks is 2 for that. 

 

Is my logic right? 

[General Zodd]

That’s how I’d read it, doubling the base number first, then adding in additions afterwards. I don’t know how bullet proof that rules reading is, but that’s certainly how I’d play it myself!

[Dagoth Ur]

My gut instinct would be to first apply all multiplicative modifiers, then all additive ones.