Kajukabla, you did say "threaded" so I apologize if this is off topic, but I love my HW44. It's not threaded, but the suppressor comes off by loosening the set screw. I got quite an education when buying it though. Export laws on those require that the manufacturer secure the suppressor, so they put some Loctite (or similar) in there. AoA made it clear to Weihrauch that they didn't want any that couldn't have the suppressor removed, so apparently they use something equivalent to the blue Loctite as hitting it with a heat gun will allow you to loosen the screws. Based on a post here, I bought mine from Krale. If you buy there, the suppressor comes in the box with the gun, not attached. Just tighten the set screw.
As for Krale, it was the first time I had ordered there. Shipping was lightning fast, and even after paying the import duty/tax it was still cheaper than buying from AoA.
Edited: CRAP! I'm sorry. You said CO2. Apologies.