40mm Beehive round

[Legbreaker]

A look at the "key to abbreviations and symbols" for the document confirms "g" is grams and not grains.
Looking at the cut away diagram it looks like it could be reloadable too with the right equipment and supplies. Not something you're going to be doing in the field, but pop out and replace the old primer, throw in some new propellant and cap it off with something to replace the copper disk and you're good to slot in replacement projectile assembly.
Not much more complex than reloading small arms ammo.