The 3.7 inch Anti-Aircraft Gun in Canadian Service Book Review

By Cookie Sewell

Review

Canada, like Britain, became aware of the need for antiaircraft guns just prior to the start of the First World War. While Canada had but one antiaircraft battery in France during the war, equipped with 10 3" 20-cwt British AA guns, it was the start of a new branch of artillery. But it was a crude and ineffective weapon and system: out of 15,832 hostile aircraft observed, 5,433 were fired on but only 16 shot down.

There are a great many reasons for this failure, and Canadian artillery expert Doug Knight patiently and clearly explains them in the first part of this fascinating little book. Trying to hit a moving object that is moving in three directions at once and is at a considerable height requires a lot of mathematics and prediction of where it will be when the shell arrives; the fuse on the shell must be properly set, the lead correct, and the shell has to arrive within about 10 meters of its target at detonation to have fatal effect.

To try and provide better changes, a more powerful weapon was needed, and starting in the late 1920s the British came up with the 3.7" AA Gun in 1938, and it became their standard heavy antiaircraft gun for the duration of WWII.

With an effective ceiling of 32,000 feet, the 3.7 was roughly equivalent to the US M1 90mm gun and the German FlaK 18/36/37 8.8 cm guns. It fired a 28 pound projectile with either high-explosive fragmentation, shrapnel, or armor piecing capability. (Shrapnel was originally felt as useful against low-flying aircraft; while the British abandoned the projectile in 1943, it is interesting to note the Soviets introduced their 3Sh1 and 3Sh2 projectiles in the 1970s for artillery to deal with attack helicopters, and are still working on tank main gun rounds for the same purpose.)

Many armchair experts always have loudly bemoaned the fact that whereas the Germans adapted the 88 as an antitank gun, and the US eventually modified the 90mm gun as a tank weapon, the Commonwealth never wanted to use the 3.7 as an antitank gun. Part of that is explained here as the very fussy and complex chassis, beside being heavier than most, was not suitable for quick changes of firing position nor capable of behind fired from its carriage in travel mode as the 88 was. (The gun was eventually adapted for use on the Tortoise heavy self-propelled antitank gun, and Doug also covers the short-lived career of the Ram SP 3.7 project in this book.)

As Canada quite often – and without similar fanfare to the US – served as the impregnable arsenal for England, starting in 1939 they began production of 3.7" guns and spare barrels for the Commonwealth forces. By the end of WWII Canada had produced 3,479 weapons, and another 5,129 barrels for the war effort. Yet in all this, once more Canada wound up with but a single mobile regiment of AA guns - 2 Heavy Anti-Aircraft Regiment, RCA. Spending most of its early time protecting a stretch of Essex east of London, by the time the regiment got to the continent in 1944 it was adjudged that the Allies had air superiority, so it wound up being used for fire support instead (the gun had a surface-to-surface range of more than 20,000 yards).

After the war the 3.7 remained in service with the Canadian Army in active and reserve status until 1957.

Overall this book is a great little read and is also useful at explaining antiaircraft fire control to the layman.

Thanks to Clive Law of Service Publications for the review copy.