Ian McCollum posted a video on SVT-40, talking about its seminal gas system, among other things, but he neglected to mention one of its most unusual features: the barrel has no gas port. The front part, which includes the gas diverter and the set for regulator, front sight tower, and the muzzle brake, is made in one piece, and attaches to the actual barrel as a muzzle device. Heck I think it's not rifled.
The gas port phobia around the 1930s was a real thing, and that is why early Garands and G.41 had gas traps. But in case of SVT-40, there's no trap as we recognize it, only a barrel extension.