I understand what you are trying to do but it would be easier just to buy a 5 LB CO2 tank

you need  a normal CO2 tank male to the same thing, in a coupler or short nipple

info on goggle I have not found yet

I will keep looking 

well the thread size is CGS 320 and that is 0.825 - 14 NGO

still working 

I can't find any CGS 320 products that are male, all are for hocking to tanks make them female and no help to hook to the FWB female pistol tank adapter and then have a female thread size to your 20 oz tank

I'm back to my original conclusion buy a 5 lb co2 tank and bite the bullet or find someone to make the adapter but at what cost I don't know

good luck about all I can do but it has been a fun search, I always learn something and that is my reward

take care

well you could build of this part and make an adapter

https://www.arc-zone.com/adapter-1-4-cga-adapter?gclid=EAIaIQobChMIvuDF8o6L2wIVCNVkCh0PJAaCEAQYAyABEgIfSPD_BwE

just for thread size info

https://www.amazon.com/CGA-320-Nipple-Washer-Dioxide-Fittings/dp/B06WVMF9PV

Paintball is about 0.811" od - 14 male.

FWB is about 18mm (0.71") od - 1.5  male.

Thanks for the help. I'll take my brass FWB adapter to the store to see if it fits the 5 pound tank valve.

well it should, when looking into buying a bulk fill adapter for a Aeron Brno  B96 they had 2 different thread sizes for full size CO2 bottles, one being European and one being Canadian-USA versions

the adapters are still available for the FWB co2 models in any case

I did see that there was at some time a FWB conversion tube that took 12gr cartridges but was never able to get much information on it other then someone made one or bought one made

but that 12gr tube would be my choice to replace bulk fill, just because I'm lazy 

here is the post on that 12gr conversion, it is not much different then the single 12gr cartridge adapters that you can buy for the 88gr tanks, I made 2 up for my Hammerli 850's, for testing or a short shooting afternoon it beats stuffing in a 88gr tank

the post

https://www.armas.es/foros/aire-comprimido-airsoft-segunda-mano/feinwerkbau-c10-super-vendida-1039168

more info useful or not

http://www.mp3.xyz/fwb-c5-Ru24rojtGeB.html

https://www.pyramydair.com/blog/2015/12/feinwerkbau-model-2-target-pistol-part-2/

I was thinking of making something like that shown in the video you provided except using paintball tanks (I use them to fill my crosmans).

these parts are something that could be used in making a single 12gr cylinder up for the FWB 2

https://www.ebay.com/itm/Quick-Change-12g-12-Gram-CO2-Cartridge-Adapter-with-88g-Bottle-Threads-Black/312135269585?hash=item48acb63cd1:g:Ni4AAOSwj-Ba-6OR

https://www.asap-supplies.com/us/faria-threaded-bush-adaptor-707411

trail and error would be in the mix but the Ebay part is a good unit, it pierces the 12gr cart and goes straight through, the sender adapter would need to be tapped for the adapters thread size, which is 16mm x 1.5

epoxy the front of the single cart hold together with the sender adapter after thread work is done, no leaks  and put an o-ring on the sender unit

you might have a cheap way to use 12gr carts with the pistol not bulk fill but an option

the Ebay adapter is 24.40mm in diameter

just ideas and I will give this dog bone a rest

take care

mike

Thanks for the ideas.  I'll let you know what I come up with in a couple weeks.

The FWB adapter came today so i know the thread size.  I ordered this today from Ebay:  

CO2 Paintball Tank CGA 320 Adapter

well that looks like the key to solve your problem, way to go

take care

mike

Tried to add a couple pictures .  ? 

It worked!  (Adding pictures that is).   I had to drill out the fitting to 1/2" to clear the filter on the FWB gasket. Thanks for the help.

  OOPS!!