[code]
Firing in a
a-a-a-a-a-
-b-b-b-b-b
gives you a recoil of
1111111111
whereas
a-a-a-a-a-
b-b-b-b-b-
gives you a recoil of
2-2-2-2-2-[/code] that's probably the reason why it's alternated, but the amount of rounds put out is actually double. The rate of fire of the bolter is way lower but in more detailed games marines have a special skill that lets them fire twice its normal output if they are standing. Since I doubt that the mechanical features of a bolter are altered by the marine feet position, I have to guess that it is because they actually score more hits. So it was acceptable to me to think that a marine able to fire full auto with a decent precision could be translated in assault 2.
Rate of fire-wise I put weapons in this order:
heavy 1
assault 1
heavy 2
rapid fire
assault 2/heavy 3
assault 3/heavy 4
and so on. Of course it's pure speculation, but I feel it's acceptable enough.
Now that I listed it I notice how small is the "distance" between rapid fire and assault 2, but I still like the "rounded all corners" better than "it's fasterer!".