[Fyron]

Having more weapons also means you have more chances to miss. If you have 50 heavy mount weapons and a 25% to hit rate, you will on average hit with 12.5 weapons. If you have 100 unmounted weapons and a 25% to hit rate, you will on average hit with 25 weapons. If the first set of weapons is doing 1.5 times as much damage (as heavy weapons in stock do), you will do 37.5x damage (where x is damage from one unmounted weapon). Now compare to the 25 unmounted weapons that hit, you do 25x damage. Which is better?

If you only have 3 or 4 ships, you might occasionally see a return with the mix of weapon mounts. But when you get any size of fleet, it averages out to make the unmounted weapons less than useful.