This guy is missing important thing. Piston ring is not tapered as hi said. Its outer surface is a sphere segment because piston is swiveling while going up and down. His ring has cylindrical outer surface. It easily brakes because it is mostly running on its edges.
Yes, he should be sponsor. He might learn something here.
IIRC from his extensive posts on the AR forums regarding material and shape, the ring he sells HAS a radius - i.e., not cylindrical. In the video he mentions that the cylinder bore is tapered, perhaps that's to what you are referring Misha. I that's true, it's beyond my understanding.