One hit to any firearm or AA gun would most likely render it inoperable. Again, not to mention 50-100 hits.
That's quite irrelevant, as the 'durability' of objects set by the game is at an arbitrary point which HT deems suitable for gameplay.
Remember that we have a CV that takes 8,000lbs to kill, when in real life few 500lbers might be able to sink a capital ship. We also have a light hangar construction which takes quite a few 1,000lbs bombs to kill. Pretty tough for a thin-walled, unarmoured, wood/aluminum structure I'd say.
So, whether a firearm would be damaged with one 50cals or one hundred 50cals, is a moot point.
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The only thing that matters is how many rounds it is currently required for a .50 round to hit and destroy an ack.
One or two 20mm HE round with a grenade type of blast effect can destroy a single ack in the game. According to scJazz's testings, a typical 20mm round is abour 3~4 times more powerful than a typical .50 round.
So, it would require 3~6 direct hits on the ack with a .50 round to kill it. If we assume a middle point and say it takes 5 rounds of 50cal hit to kill a single ack, a typical average pilot with 5% gunnery accuracy needs to fire 100 rounds to get just those 5 hits.
You call it BS, I call it simple logic. Acks are very small targets. They are stationary, but also very thin.
The fact is, people aren't just as accurate as they claim to be when they shoot at the ack. Nor do they have a clue as to how much rounds they are really landing on the ack.