I haven't seen that. Maybe they did, but carrying bombs AND all that ammo would have made take-offs exciting. I'm not sure where that much ammo would have been stored if not in the bomb bay. B-17s aren't that roomy inside.
Most of that normal load was carried near the gun positions. But the ammo canisters for a waste gun (600 rds late war) were huge! If you were to triple that and add a second gun at each window . . . it's going to be really tight, if not impossible to cram that all in there.
Yeah. But if all of that ammo just went to a reserve in the bomb bay you wouldn't have that problem. Whichever position needed the ammo could be resupplied in flight. Of course that wouldn't have been an easy proposition.
I suppose it would be, but hitting the bombs in general would be a hard task, especially at night. I don't think the fighters aimed for the bomb bay, it was just a lucky hit if you managed to detonate one or bad luck if you were in too close proximity.
German night fighters using Shrage Musik got in pretty close. They took extra care to hit the wings (with the engine and fuel tanks) rather than the bomb bay for that very reason.