How do you know bullet 2 hit first ? I'm not convinced. If it was a stub nose or hallow tip you wouldn't know, the whole window would shatter. I think there will be more cracks then that. Most windows are shatter proof so they shatter like small spider webs all around the window. Either that or it shatters completely. That is why when someone breaks into a car you can't use a bat you need something with a small tip. Small tips with a lot of force behind it will shatter a shatter proof window. Without shatter proof the whole thing would just shatter from anything no matter wide or narrow. So a bat would shatter the whole window.
Also recoil climbs and goes side ways. Bullet number 1 looks like it would hot first then the recoils starts to climb. Bullets never ever go top to bottom .
you are overthinking all of it and you are also wrong about it all.
it is all about Fracture Mechanics.
propagation of a crack in a brittle material to be exact. in general when a crack reaches a stop (here it is another crack) it stops unless there is more force which will shatter the glass.
so when the cracks which were started from 1 or 3 reach the
pre-existing cracks of source 2 they stop.
you can read more about this in fracture mechanics part of Dieter's book
hahah. you nailed it. i don't where he get his conclusion. but anyway i support the #2 bullet for best answer. i already read the fracture mechanics part of Dieter's book during my college days and it is clearly see in the picture that the cracks made by bullet 1 & 3 didn't ovelap or transverse in the crack made by bullet #2. The impact didn't transfer in that part because of discontinuity of material.
I think JasonXG gonna say again that i'm rude.
peace brother, i'm just always carried away by your post. that's all