Library 2F - Castle Grand Hall 1F (Resident Evil 4 Remake)

On the table on the west side of the main room.

Inside the Square Lock Box on the eastern wall, but only if you do not already own this weapon. You need to use the Cubic Device to open it.

Inside the Square Lock Box on the eastern wall, but only if you already own the CQBR Assault Rifle. You need to use the Cubic Device to open it.