Another vote for "two two three"
I offer a parallel:
DROP FIVE-ZERO
FIRE FOR EFFECT, OVER
(Or for the 08s, "-50, FFE k", for non-08s "reduce the elevation of your howitzer so as to bring the impact back fifty meters, and fire all six guns, thanks.")
I'm not quite sure what the technical name is for the military habit of referring to numbers individually (until hundreds and thousands), but saying "fifty meters" will cause unpleasant things to happen to any artilleryman.
I suppose I do say refer to guns as "forty-five", "forty-four", "three-eighty", but I also consistently say "two-two-three", "five-five-six", "seven-six-two", "three-five-seven mag".
Come to think of it, I also say things like "seven-six-two by fifty-four rimmed". I guess I have no truly consistent system, but I am set in what I say for each particular cartridge.
-MV