Hi there
I've just read something quite interesting and ... funny to say the least, about french artillery calibers after 1801.
In 1801, Napoléon reorganized the artillerie, and updated most of the regiments. New organization, but also new guns.
The standard french 6 and 8 lbs guns were kept, but a small modification was made to the canon balls.
Instead of being 6.0 or 8.0 lbs, they became 6.001 and 8.001 lbs.
It became quite common before 1801 for the french and Austrian/Prussian to steal each other canon balls during battles.
By making the caliber of the french artillerie slightly bigger, the french were still able to steal Austrian or Prussian canon balls for using in their own guns -with a small accuracy loss because of the smaller canon balls though- but Austrians and Prussians werent able to put french canon balls in their own guns
It's funny to see such a move from the man who brought the metric system to Europe -and the world!-