I know how to make custom portal guns and have made a few earlier, however today I wanted one that would be partially transparent as to see whats behind it but couldn't figure how to do it. I also know this is posible because i've seen a few videos with it like the chamber 13 save glitch guide by crisper.

https://files.catbox.moe/96etxl.vmt rename it to v_portalgun.vmt put it into your unpack/portal/materials/weapons/v_models/v_portalgun