Why is it called “20mm” if it is reportedly 19mm?
Vlad, you need to measure the projectile on the bourrelet and not at it’s base.
Thanks for reminding me how senile I’ve have become since 2011. I was reading a 1974 War Monthly article about Oe development by Ian Hogg, which said that Stahlwerke Becker sold the design to Maschinenbau AG Seebach of Switzerland (because of Versailles Treaty, and the Swiss changed 19mm into 20mm. Not remembering what I did 2min ago, I asked the question. Great magazine, by the way, for people like me.
Vlad, actually not. The Becker is 20mm.
SEMAG was a bypass of the Versailles dictate and as you say later sold to Oerlikon.
As said measure your projectile again.
Hogg’s many books are good value, especially for the larger calibres (he was an artilleryman by trade), and he is one of the few military gun writers to have given proper emphasis to ammunition. But everyone makes mistakes - even me!
I’ll agree that Mr. Hogg is a fine historian, but he does have his favorites. I do remember reading one of his books and he stated flatly that he highly doubted that the U.S. M1917 Rifle was ever used in combat. Later pictures in the same book showed French troops in the southern invasion doing combat operations with them. Cheers, Bruce.