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Furthermore, the bulk of the 3" guns were used at home, where the enemy raids were largely at night. From this arose the widespread use of barrage fire which resulted in heavy ammunition expenditure and consequent wear of the bore. The life of the barrel was only some 1,500 rounds, so that replacement or relining of worn-out guns became a serious problem. The gun was provided with a two-wheeled carriage for moving, but this had a low road- speed and very little cross-country mobility.
3*
ith these disadvantages, it is natural that the equipment, like all other .. guns, emerged from the war with not a very high reputation; but, during the post-war period, remedies were found.
The introduction of the Vickers predictor turned an ineffective weapon into an accurate gun; a system of removable liners obviated the disadvantages of barrel-wear; and the introduction of a four-wheeled carriage, from which the gun could fire, gave it a considerable degree of mobility, both on roads and across country.
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With these improvements, the 3 gun was perfectly adequate for its role until the development of the high-speed monoplane. This introduced new factors which had not previously existed. The latest aircraft types were able to fly without difficulty above the effective ceiling of the 3 gun (18,000 feet); improvements in bomb-aiming opened up the possibility of accurate bombing from such heights; and the long times of flight of the shells to the higher altitudes facilitated avoiding action on the part of the enemy.
5.
These developments gave rise to a demand for an A.A. gun with a higher ceiling, a shorter time of flight of the shell, and a bigger effective radius of burst of the shell. The demand was met by provision of the 3.7 gun, but its increased size and weight resulted in a reduction in the rate of fire and rate of traverse, and considerable loss of mobility.
6.
Comparative figures are as follows :-
3"
3.7"
Effective ceiling in feet. Rate of fire in rounds
18,000
25,000
per minute.
20
12
Time of flight to 10,000
feet in seconds.
10
7
Effective radius of burst
in feet.
Rate of traverse.
30 1800 in
5 secs.
45 1800 in
20 secs.
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