Exactly, using lead balls to a pound weight is a gauging method.
A bore is a hole.
The bore dimensions of a 12g is nominally .729" but can vary from .710"-.740".
That is why the term guage should be used and not bore.
Wait, YOU GUYS taught US it was referred to as "bore". See The Sporting Rifle and Its Projectiles by Captain James Forsyth, British Army, India 1867
Today..., you guys tell us,
It's a spanner, not a wrench
It's a bonnet, not a hood,
It's a boot, not a trunk,
It's a wagon, not a train-car,
It's a lift, not an elevator,
It's a pram, not a baby-carriage,
It's a bumpershoot, not an umbrella,
It's a wireless, not a radio,
It's vit-a-mins, not vite-a-mins
It's al-loo-min-ee-um, not al-loom-in-um,
It's la-bor-a-tory, not lab-ra-tory,
It's a lavatory or a loo, not a restroom
EGAD!
LD