@ballplayer72
I am counting the thirty bullets as weapon 7, not a single bullet; a single bullet wouldn't break down a wall. Sort of like an AK-47 is weapon 3 for a burst, not a single bullet.
@YuriPup
Assume a PC with supernatural toughness and an athletics as good as the equivalent attacker's skill plus endurance +3. That PC could be "Feet in the Water" and still have refresh left. The following are true;
1) The PC has a stress track of 8 boxes plus armor 2.
3) A normal hit from the attacker's GAU-8 is going to do 7 stress; 7 from the GAU-8 weapon rating plus ignoring 2 armor from AP rounds.
4) The GAU-wielding attacker needs to score 3 average hits for a takeout or get really lucky.
Now let's do the same math for a normal tank;
1) The tank has mythic toughness, hulking size and thus stress track 12 and armor 3. (it also has physical immunity to weapons 3 or less but that's irrelevant)
2) A normal hit from the attacker's GAU-8 is going to do 11 stress; 7 from the GAU-8 weapon rating, -1 from the tank's armor which is reduced due to AP rounds, +4 from the attacker's skill since the tank has no athletics skill to dodge plus a +1 due to hulking size being easier to hit.
3) The tank is going down in 3 average hits or one really lucky hit.
So, as you can see, a "Feet in the Water" tank is just as hard to kill with a GAU-8 as a normal, mechanical tank. Yes, a trained gunner is going to have stunts to improve his skill with weapons and thus kill both tanks in one burst each but we are talking Feet in the Water here. A submerged tank is significantly tougher (the submerged version of Valera could survive over twelve average attack rolls with her defenses)
And the Submerged Valera is neither strong enough nor bulky enough to use the GAU-8 yet. Her 20-refresh version? Certainly.
@tymire
The GAU-8 is not an automatic weapon, it is not chain-fed or clip-fed (it takes individual bullets) and was made with anti-jamming in mind. Once you remove the hydraulic/electric rotors and replace them with a hand-moved rotor that a superhumanly strong character could move, you've kicked the tech back to 1860. Yes, THAT far back. Only a very powerful wizard could jam it and only if he was intentionally trying to hex. And yes, the 20-refresh version of Valera took that into account.