Came across these two while doing research for a build down the road.
https://4shooters.com/product/custom-guns-gk-04-vepr-12saiga-12lynx-12-muzzle-brake.html
https://ishooter.ru/product/dtk-ilina-gk-05-custom-guns-pravii.html
Any independent testing on them? I was originally under the impression that the GK-03++M was the absolute state of the art, and only tied with the V6 brake.