[4] In 1908, on the advice of Professor Carlo Bourlet, he established a laboratory for aerodynamic experiments in the garden of a retirement home founded by his parents-in-law in Levallois.

During World War I, Gramont was a motorist interpreter with the British Army Corps, then an aviator in the Technical Section of Aeronautics where he met the scientist Henri Chrétien.

As an industrialist, with the ambition of competing with German production, he founded in 1919 and managed the company Optique & Précision de Levallois (OPL), which took over from the optical device manufacturing workshop.

In 1938, Armand de Gramont, wanting to diversify OPL's production towards the civilian world, had a factory built at Châteaudun in Eure-et-Loir.

Together, they had five children:[10] A rare film clip shows Proust (in bowler hat and grey coat) at Gramont's wedding in 1904.

[12] Proust’s wedding gift to Gramont was apparently a revolver in a leather case inscribed with verses from the bride’s childhood poems.