Yeah, if a luftwaffe pilot found a lone bomber they gladly attacked it rather than a formation of bombers.  Being a gunner on a bomber must have been a tough job I believe.  Aerial gunnery in real life was probably much much more complex and difficult than we have here in AH.  It was probably much harder to aim a gun in a bomber in real life due to vibrations, air currents, and recoil.  It really depends on the skill level of the gunner I think.  As for 20mm and 30mm not killing bombers in 1 pass, thats understandable.  It depends on where u hit the bomber.  A bomber has alot of empty volume inside of it, a 30mm shell could simply pass through the waist area of a B17 and not do much critical damage.  Of course we have probably all seen the picture of the B17 with its tail nearly severed by a mid-air collision with a 109.  This shows that unless hit in the right spot, bombers could continue to be airworthy.  I have seen the gun cam of the B24 hit in the wing root by flak, it is really spectacular (the color version).  I don't think that any of the crew was able to bail out, probably due to the g forces.  After the war a study was done on bomber defensives.  It was concluded that in order to shoot down a single enemy fighter, that 5 B17s needed to have 5 guns firing on the target with 50% accuracy.  Of course in real life B17s averaged only 1 pair of guns on the target with only 10% accuracy.  As for the convergence being slow in late war bomber/fighter combat, thats the opposite of what I have noted.  Even with piston engined 109s and 190s, head on convergence was usually around 600mph, too fast for the bombers to get off more than 1 or 2 shots.  With the addition of the 262 to the luftwaffe,bomber gunners complained that they didnt even have time to line up the fighter in their sights.