Sorry for the necropost, I never see these interesting threads when they are live
I considered that cross-location ammo feeds would be like those motorised roller conveyors on production lines, a shot's worth of shells/missiles is pulled from the ammo bin and pooped across from one torso side to the other (for example) so the feed isn't permanantly full of it.
Generally you'd see advantages in reliability and maintainance if ammo was stored in the same section as the weapon as close as possible to it. This convention might be suspended in the case of putting an autocannon in an arm to get a better range of travel but putting its ammo in the adjacent torso somewhere at the back to protect it better and mitigate ammo explosion damage to the arm if other weapons are located there. It'd not be any fun to fix though