It is really close to 3/8"-16, however the 1.5mm thread gage..............

fits the latch rod thread perfectly and not a 3/8"-16 thread. A 3/8"-16 bolt will screw into the piston but binds before getting 1/2" deep.

Actually, I think that the thread AA uses for the latch rod is a "close class fit" which is why it won't thread into my 10x1.5mm die.

A fellow on one of the UK forums suggested that I split one side of my 10mm die so it will cut a slightly larger diameter thread.

Oh well, perhaps it's time to learn single point threading! Hummm....I'm wondering how hard is it to grind a bit to cut a thread?