In Alexander Freed’s Alphabet Squadron novel (which is fantastic, by the way) the total firepower of the B-wing Starfighter is stated to be enough to vaporize a small mountain.
Context and Excerpt
In the final battle of the book, the New Republic’s Alphabet Squadron attacks Orbital One - a Tibanna gas mining station of the planet Pandem Nai, which has been taken over by the 204th Imperial Fighter Wing (also known as Shadow Wing).
The B-wing of the squadron, piloted by the character Chass na Chadic, is tasked with blasting the hangar bays of Orbital One, so as to prevent or delay the launch of Shadow Wing’s TIE fighters. During her attack runs, she crazily starts blasting away with all her armaments (laser cannons, auto-blasters, ion cannons, proton torpedoes).
B-wing total firepower is described as such:
She felt a flash of heat, heard the sizzle of the cannons and a series of pops that brought the music to an abrupt end. She smelled components melting as destructive energy poured from the four points of the starfighter’s cross, filling the viewport with sun-bright particles capable of vaporizing a small mountain. She kept squeezing as, one by one, instruments turned red on her console. But she heard no terrible thunder - she couldn’t see through the firepower she’d unleashed, but she’d have known if the gas pod had detonated. Wouldn’t she?
~ Star Wars: Alphabet Squadron
Just how much firepower is that?
Lina Shields had made a blog detailing the amount of energy required to destroy mountains of multiple sizes by multiple methods.
The energy needed to destroy a small mountain of height 609.6 metres (which is the baseline height requirement to qualify as a “mountain”) is 4.9 Gigatons. That is close to baseline 6-C (Island level).
Is the statement reliable?
Now I know this might seem like hyperbole. But I don’t think so.
In the Canon story Blade Squadron: Zero Hour, the B-wings of Blade Squadron unleash proton torpedoes which unleash pillars of flame that consume a Moff's palace and estate and even an entire valley:
"Stay in formation," she said. "We're only going to get one pass." The B-wings roared into the grass-covered valley that contained the sprawling estate. The barrage of torpedoes turned the various buildings into pillars of flame, which then collapsed in on themselves. In moments, the whole valley was a roaring inferno.
~ Star Wars: Blade Squadron: Zero Hour
And I would like to add that palaces and estates in Star Wars can be massive by real life standards. Palaces can be the size of a mountain while the estates can be the size of a small city. Palpatine’s palace on Coruscant in Canon (which is the former Jedi Temple) is over 1 km tall and wide (official figure) and has a landing strip in front of it which can accomodate star destroyers. The castle of Queen Trios of Shu-Torun is the size of a mountain. And there are other administrative buildings throughout Star Wars that are massive. The Senate on Coruscant is over 2 km wide. The New Republic Senate building on Hosnian Prime is at least 1 km wide.
We also have this feat where half a mountain is vaporized (albeit from a star destroyer’s turbolaser):
We also have a plethora of vaporization feats for weaker, comparable, and more powerful weaponry:
Refer the last paragraph in particular. The MG9 proton torpedoes used by B-wings should be more powerful than the proton torpedoes and concussion missiles used by strike fighters such as the TIE/sf of the First Order. The MG9 was meant to be used against capital ships. So it makes sense that a B-wing's total firepower approaches the power of a capital-grade turbolaser blast.
B-wing vs Quasar Fire
Earlier in the novel, during one of the final battles in the Oridol Cluster between the Hellion’s Dare (a New Republic EF76 Nebulon-B escort frigate) and the Aerie (a Shadow Wing Quasar Fire-class cruiser-carrier), Chass and two of her fellow B-wing pilots make an opening in the Aerie’s shields with their ion cannons, then Chass unloads on the Aerie’s rear with all of her B-wings weapons.
The cruiser-carrier was close enough to dominate her view. She cut short her barrage and turned, swinging the cross-body of the fighter to reposition her jets. Now she was passing over the carrier. Now she was a perfect target, and she could see her objective. She fired again and unleashed the B-wing’s entire arsenal, proton torpedoes and laser guided bombs tearing through space as her shields burst and particle bolts scorched metal. She smelled burning wires. She heard Glothe scream and his blip fade from the scanner.
Far below, lightning raged over the rear of the cruiser-carrier. She shot past the vessel and checked her readings.
“Direct hit! Direct hit!!” Mesh called.
“Quasar Fire’s lost power to its engines,” Chass said. “They’re not following us anywhere.”
~ Star Wars: Alphabet Squadron
Quasar Fire durability
The Aerie was severely damaged by that barrage. She lost engine power, hyperdrive capability, and all combat capability. However, she survived, was still space-worthy, was repaired by her crew, and returned to the planet Pandem Nai later on in the book.
The Aerie essentially survived (albeit was severely damaged) enough firepower to vaporize a small mountain.
I am of the opinion that the Aerie does not really deserve a durability rating of baseline Island level (without deflector shields) seeing as how she was almost crippled by that kind of firepower. But she did survive. Something like Large Mountain level or Large Mountain level+ seems more fitting.
I would like to add that this is all oddly consistent with the accepted end for this feat, which is the source of the current Large Mountain level+ durability rating for many Star Wars capital ships. I would also like to add that the proposed durability rating for the Quasar Fire-class would be oddly consistent with the current durability rating for the Arquitens-class Light Cruiser, which is - funnily enough - in the same size range as the Quasar Fire-class. The Arquitens-class is 325 metres long and the Quasar Fire-class is 340 metres long.
ISD2 vs Quasar Fire
In the Canon comic series Star Wars: TIE Fighter (Issues 1 and 2) the Imperial II-class star destroyer Celerity disables and destroys the Quasar Fire-class cruiser-carrier Summit.
In Issue 1 the Celerity first disables the Summit with a heavy ion cannon blast, knocking out her shields and primary hyperdrive. In Issue 2 the Celerity obliterates the Summit with just two turbolaser shots.
Note that the shots came from the prow of the Celerity. Those were not her most powerful cannons.
What does this mean?
It means that a twin turbolaser blast from an Imperial-class star destroyer has far greater power than the total firepower of a B-wing starfighter. Whereas a Quasar Fire-class can survive baseline Island level firepower with severe damage, but with her hull mostly intact, still be space-worthy, be repaired by her crew and then be on her way again; a twin turbolaser blast from an ISD can outright blast the whole ship apart (you can see in that scan that the Summit was torn into three).
Total firepower of all B-wing starfighter’s weapons:
= Around 4.9 Gigatons = 6-C (Island level)
Quasar Fire-class cruiser-carrier durability:
= Likely High 7-A (Large Mountain level+)?
Celerity obliterates Summit with a twin turbolaser blast:
= Far greater than 4.9 Gigatons = 6-C (Island level)