firing

I am having a discussion with someone who tells me that spitfires equipped with 2 Hispanos and 4 Browings, could only fire all 6 weapons at the same time or the 2 cannons, but not just only the Browning guns. Now I can argue that the 3-position firing button didn't have 3 positions for nothing...

Reading the thread on "ship busters" for ww II and the mention of B-25s with 75mm howitzers, that reminded me of this: Has anyone else seen this before? http://www.dtic.mil/dtic/tr/fulltext/u2/750150.pdf It's basically a CH-47C with two externally mounted forward firing 105mm howitzers.