It really does depend on where the bullet hits. there was a reported case of either a spitfire or hurricane landing on the dunkirk beaches after d-day when it recieved ONE bullet hit in the glycol header tank which was situated just behind the prop. there were other cases of ME109s being downed with a hit in the fuel tank and as the pilot is virtually sitting on the tank in those machines i wouldnt fancied that!!! - too much fuel for the cigarette lighter old chap!!