This reminds me of a flat of non-US made ammunition I bought a few years ago. This was very powerful and heavy recoiling ammunition made in Denmark. I only purchased it because it was incredibly cheap. I used them on a pheasant hunt on one occasion in my Brno SxS in 12 gauge. My hunting partner and I later dubbed the shells the "Hammer of Thor" given the recoil and the effect it had on the rising rooster.