qnli question: What was the practical ceiling of the effective heavy guns? sentence: Of the "heavies", some 200 were of the obsolescent 3 in (76 mm) type; the remainder were the effective 4.5 in (110 mm) and 3.7 in (94 mm) guns, with a theoretical "ceiling"' of over 30,000 ft (9,100 m) but a practical limit of 25,000 ft (7,600 m) because the predictor in use could not accept greater heights.