28.35 grams = 1 ounce Av.
http://www.metric-conversions.org/weight/grams-to-ounces.htm for a converter where you plug in the number of grams and get back the number of ounces. Answer: 28.35 g = 1.00001 oz. from the converter.
On the question of AYA making tubes - I suppose that refers to choke tubes, maybe John Boyd will respond. My guess is AYA does not make them, and that Briley or Teague choke tubes are the main ones installed if a customer wants them.
A video about Mastering the Double Gun showed a couple of E.J. Churchill guns that must have cost five or six figures that had Briley choke tubes installed. If they knew of anything better, they probably would have used it.
My guess is that if a gun is ordered with choke tubes, it gets built (maybe with no choke work done to the barrels), imported, sent to Briley for the installation, then back to the importer to be delivered.
