Where and when were guns and cannon on replacement aircraft sighted in?

[Broncazonk]

The title sums it up. Where and when did replacement fighter aircraft go through the process of having their tails jacked up and their guns and cannon fired and adjusted for range and convergence--at the factory, at a supply depot, or after the aircraft was delivered to an operational unit?

How 'combat ready' were replacement aircraft when they arrived at a unit? How much work did the black men have to do to get it ready?

Thanks!

Bronc