Hey Bruno, when was the last time you flew AH? Just curious, because that info is wrong on 100lbs. It takes 1 cannon round. It's only ever take that much. You might fire a short burst of 3-5 to get the "1" to land on target, but it only takes the one then "Poof!" "SYSTEM: Soft Auto Gun Destroyed"
Ask anybody that's deacked a field. I don't think the numbers on that page have been updates since AH1 went public. Look at the amount required for hangars, and for the HQ. 250lbs for a barracks? Well I know an la7 can strafe them down with 100 20mm rounds, that's nowhere near 250lbs.
So those numbers don't apply anymore
As for the weakness of the MGFF, yes we all know they're the worst of the 20mm. But they are still 20mm. I think that was the original point.

EDIT: Oh, P.S. about the 190A5: I know! Ugh! I wish we had the 90-round drums. I requested it a long time ago (years ago, I think) but alas, no response.