Thread size Crosman Airsource

Does anyone know what the actual thread size is on the Crosman AirSource cartridge?  It appears to be 5/8" od (I get .615 with a mic) but laying a 18tpi thread gage on it doesn't match  is it a metric pitch by chance?

Cheers
Mark

If anyone is interested in making custom adapters for reference.

I found a thread in the Crosman Gate on Airsource thread size, it's apparently 16mm (.629") by 1.5mm pitch (close to 17tpi).  Use-Enco.com has that in stock (tap & die) so its not an oddball size.  Someone mentioned Crosman has them made in Hungary.

If I read it correctly the Paintball tanks I have are 7/8" x 14tpi another standard stock item.

Cheers
Mark