It’s been a while since I’ve done one of these! Here’s a link to the previous edition.
Q: I found these on EnglishRussia, and there is a KV-2 turret on the IS chassis. Can you tell me more about this?
A: It is a movie prop, and one of dubious quality at that. If you look further, you can see “KV-1″ tanks that won’t fool even a casual observer. For instance, their guns are clearly immobile.
Q: Is there some pattern to gun calibers? Several nations seem to use the same ones, 20 mm, 37 mm, 75/76 mm, 105 mm, etc.
A: A lot of gun calibers are in multiples of inches. 37 mm is about 1.5 inches, 76 mm (76.2 mm) is 3 inches, 152 (152.4 mm) is 6 inches. Doubling your shell’s diameter has an easy to calculate effect on its vital properties, such as weight. This lets an engineer get close to the desired performance, in theory. Of course, as he starts fine-tuning the performance, the diameter will change, so it won’t be exactly the multiple of an inch anymore. As modelling methods improved, the need to take old shells as reference ended, and modern shell designers don’t have to start with multiples of an old thing. Drastically different modern ammunition design doesn’t help either.
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