TwinBoom: That's a 20mm I believe, and what you don't say is it totally crippled the craft. It had no flight controls in the wings. The pilot struggled to get it home.
The B-26s and the Lancasters are buggy as far as damage models go. If/WHEN they are updated to modern 3D models these damage systems will be re-mapped and hopefully will end up more accurate.
I have put 5-7 30mm hits into the same localized area of a lancaster tail (on film) and posted the film long ago and many other films. The Lancasters soak up 30mm rounds like a sponge. The B-26s have a few more weak areas (they will actually catch on fire -- lancs won't) but are super-resistant to 30mm rounds.
I was very disappointed with the titanium/steel composite construction of the B-25 models. This may be a trick of perspective, but it seems the -C is stronger than the -H. I have put multiple passes on low B-25Cs in a Fw190A8 with 4x 20mm guns and hit them repeatedly over and over before finally killing them (or getting the credit when somebody else finishes them!). I've put multiple 30mm rounds into them before and not killed them. In an FSO I unloaded almost all 120 rds of cannon into one B-25C, and then out of ammo saddled up on a stationary second target. He was fixated on his target below, so I sat there at 600 yards, perfectly steady, and unloaded over 1000 7mm rounds of ammo into the same spot of the right wing root. You get 2000 rounds. When I broke off my attack I was at 400 yards, the bomber had dropped, and started porpoising and major evasive actions, with no damage for my efforts.
ALSO: I've survived multiple 262 passes in my B-25Cs while taking numerous hits from enemy guns, winding up killing at least 2x Me262 jets that made passes on my B-25Cs. These planes are WAY too strong, damage wise.
Oh, and for all those photos of "flak" hits -- most of them were duds or were not flak rounds. A direct flak hit would vaporize or disintegrate the bomber it hit. The photos folks post are so stunning because these are the rare few that survived being hit. You don't see photos of the thousands upon thousands that never made it back for photos to be taken.