Napoleon was not quoted in the posting. It was a paraphrase and having the letter and quotation would be most helpful. If it's in the Correspondence, then that would be easy to find. All I need is a reference.
Regarding Gribeauval field guns being cast, that might be an accurate assessment. However, Gribeauval siege and garrison guns were indeed still being cast after 1800. I have photographs of two in the Musee de l'Armee. One is a garrison 12-pounder cast at Strasbourg in 1810 and the other is a siege piece cast at Douai in 1802. I don't believe these are the only two Gribeauval pieces cast after 1800. The photographs are on page 92 of Napoleon et ses Soldats, Volume I by Colonel Paul Willing, published in 1984. This is a publication for the Musee de l'Armee of the collection there.
Unless you have the casting records of all of the French foundries for 1800 and after, I would suggest that you might be incorrect. Further, the seeming reluctance of both you and Paul to quote material, especially primary material, sometimes doesn't lend credence to your arguments.
Lastly, do you have any idea, since France didn't produce any tin during the period, how they cast artillery pieces of bronze/brass which requires an alloy of 10% tin?