According to the ATF letter that Pookie posted they (ATF) treat the parts count just like a milled receiver AK. (No Trunnion, but otherwise the same as a stamped receiver)
The Saiga has a floating piston and what looks like a normal piston used as a operating rod.
If the floating piston is what is considered as the piston by the ATF, as evidenced by Tromix's US made part. Why is the normal piston looking part not considered an operating rod? After all, they consider a FAL cocking handle as an operating rod in the FAL count (which is a real stretch in my humble opinion)
Here's my question. Which part is the ATF really considering the piston?