Considering distances at which they used to shoot at each other, you should notice that these planes turned extremely tightly...

for those not too far from paris, you should visit the ferté alais airfield where, usually on first weekend of june (3&4 june 2006 is the next one), you have a meeting with a bunch of WWI birds... and you can believe me, when they turn around each other, even if they are collection aircraft (and therefore, note pushed too much) they really turn like nothing else I've seen before... what's more, their maximum speeds are barely superior to take off speeds of WWII warbirds...

from there on, I guess that, to have any chance of hitting another aircraft, they really needed to be very close, say 50 yards maximum (at bigger distances, it was more matter of luck than marksmanship... considering how much these planes "move" in flight