In 1743, on his brother's death he was made royal librarian (a post Armand-Jérôme had inherited in turn from their uncle Jean-Paul Bignon). Armand-Jérôme resigned from it in 1770 in favour of his son Jérôme-Frédéric.
He was elected to the Académie française in 1743 and to the Académie des Inscriptions in 1751. He was made conseiller d’État in 1762 and prévôt des marchands de Paris in 1764. The scholar Dupuy pronounced his elogy. It was his negligence in the latter post that caused the accidents in the firework display for the marriage of the Dauphin (later Louis XVI) and Marie-Antoinette in May 1770 that left over 300 dead and a greater number of wounded. Even so, he appeared in his box at the Opéra only three days after the disaster, causing all Paris to become indignant.
Under Louis XIII, the prévôt des marchands de Paris and the two premiers échevins were fined for not having repaired a bridge whose collapse killed 4 or 5 people. Under Louis XV, his faults born of a lack of foresight were never punished. Paris thus avenged itself by bon mots against him, including the Latin anagram of his name as Ibi non rem, damna gero (I don't do good, I do evil).
Armand Jérôme Bignon never published anything, though he did leave manuscript memoirs of a journey to Spain and Italy (now held at the Bibliothèque nationale de France).
- Louis Gabriel Michaud. "Armand-Jérôme Bignon". Biographie universelle ancienne et moderne : histoire par ordre alphabétique de la vie publique et privée de tous les hommes avec la collaboration de plus de 300 savants et littérateurs français ou étrangers (in French) (2 ed.).