This post comes just handy!
I upped a Yak 9-U yesterday for some routine CAP, when one, possibly 2 dots blimp on the radar, nearby.
I thought they were IB our field, so I wanted to intercept. Then, as I approach, I see they are buffs, possibly 2 "box" of them. Actually they were 4 boxes, flying very tight, at about 12-13k.
I think that I have a fair chance to take down a couple of them in my Yak, at that height, so I don't replane, and I take the chance.
After some time chasing, 3 things are evident: they are not going for our field, they are climbing, and I am not gonna catch them under 18-20k
I start climbing after them, and in the process their target become clear: Rook HQ. I type the problem in CAPS, and 2 fellow rooks come to help.
By that time, I'm near 22k, and one of the rooks on the help start the first passing run. The Buffs formation is still as tight as the first time I saw them, and they managed to maintain a perfect box even when they turned due West. No newbies there. The fact is confirmed when I see the first rook going down in flames.
At 23k, and slightly ahead I make my first pass. Roll and dive, I'm approaching the formation really fast with a slight turn. They open fire at about 900 yds. perfectly synconized. My framerate falls to near 10, because of all the tracers. I'm amazed seeing the firepower that 12 B-17's hold. Quick pass on the front B-17, without even try to adjust. I knew if I fly straight for a couple seconds, I will be confetti. I level heading West some 800 yds below the Buffs, and very fast, and start climbing for the second pass. No evident damage....both on me and on the Buffs. Meanwhile, another Rook comes to help, and manage to score some hits on the trailing Box, before he goes in flames too. Now the trailing Box is lagging slowly.
I make another pass on the 3 leading boxes and hear some pings on my airframe. I manage to hit one of them in the wing, and one engine of the outer left plane is smoking. But I had to change tactics, as the trailing Box is falling behind and I am pinged each single time I dive on the big formation.
So I go for it, and make another pass on the last box. Now I hit him good, and one of the B-17's on the box is burning. Mind that the passes were made over 300 kts., and even in this case, these guys managed to score hits on me!. The burning Buff dies finally, and I get a kill on Addy. Another plane of his box is smoking in 2 engines, the left ones if my memory suits me well. So he won't catch up with the rest.
I switch the attack to the 3 remaining boxes to try to, at least, slow them down, and give time to my fellow Rooks to intercept. Unfortunately, Yak is not ideally suited for this task, and now my ammo is almost gone. I spend my last 20 cannon rounds. This last pass leave me with my left elevator gone, and no ammo left.
B-17's continue their run against our HQ, but I have nothing to throw agains them. One of the buffs is smoking on one engine, but they look quite OK. I proceed to disengage and land one of the most valued kills in my recent AH time, and express my consideration to Buff pilots.
They finally made it to our HQ, and manage to kill our radar. I'm glad they made it. They flew beautifully, fought bravely, and the whole fight had a resemblance of "this is what it must have been like". Keez, Addy and the rest, this was one of the most interesting fights I had in AH.
Oh!, and a little detail: they were Bishops 
