Whilst on the subject ,when did cartridge cases become "hulls" ?
Almost all modern shotgun shells are made from some type of plastic material, something introduced to the world by Remington in about 1958..(USA).....Most plastic shotgun shells have metal heads, of either brass or brass plated steel, although a few have marketed all plastic shells without this feature......... Plastic shotshells are made by either injection molding or compression molding or some variation thereof.........The compression process was developed by Winchester-Western (USA) and produces the toughest and most durable one PIECE HULLS, something of great value to handloaders.......
Paper empty cases were called tubes once upon a time....with the advent of plastic
ONE PIECE in the 1950's, they have been called hulls........
According to **Cartridges for Collectors, July 1958, Borden Publishing by Fred A. Datig...All American, British and Germans refer to brass center, pin or rim fire AMMUNITION for rifle and pistol as cartridges....shot shell empty cases are referred to as hulls..........
Most likely the nomenclature of "cartridge" for shot shells died sometime in the 1800's when all brass shot shells died out as factory loaded ammunition with black powder.......the less accurate caliber designation died as well about the same time, replaced by gauge which is a more accurate description for shotguns.
You may also use **Cartridges of the World as a reference for more detailed information on this subject......1965 1st Edition by Frank C. Barnes.....USA Library of Congress card 65-16729
*-In guns, caliber or calibre is the approximate internal diameter of the barrel in relation to the extension of the projectile used in it.....
Shotguns are classed according to gauge, a related expression. The gauge of a shotgun refers to 'how many' lead spheres the diameter of the bore would equal a pound. In the case of a 12 gauge shotgun, it would take 12 spheres the diameter of the shotgun's bore to equal a pound. A numerically larger gauge indicates a smaller barrel. This metric is used in Russia as the 'caliber number': e.g., "shotgun of the twelve caliber". The "sixteenth" caliber is known as "lordly" (Russia).
While shotgun bores can be expressed in calibers, the nature of 'shotshells' is such that the barrel diameter often varies significantly down to the length of the shotgun barrel, with various levels of choke and backboring....... 16 Grand Prix.....

12 Alpha Max Eley's.....

Cheers,