Virtus suppressor

Not sure I’m following your logic. You think that the Virtus, using 1/2x28 TPI on an airgun was a smart move? Typical airguns threads are 1/2x20.
I think it’s weird that they would use the 1/2x28 threading that is common for powder burners.
No, I was actually referring to the fact that most airgun silencers are a different thread pitch so that they can not interchange with firearm silencers. I should have been more specific in my response I guess.
 
Go to Donny FL & see their adapters. There might be one for your Sig.
I checked, here's the link:
Ok, regarding the link it appears that the 1/2"x28 bit can be unscrewed. What is the thread under the removed piece?