I have a query in to CZA as to what ammo they use for test targets. My 527 came with a test target showing a 3/8" group at 100 meters.
In the course of getting my rifle sighted in, I got a 50 yard group of 5/8" using Win cases and primers, 27 grains of H 322, and a CAST bullet from Lee C312-155-2R. That may be even better than it sounds as my dies have not arrived and I loaded the ammo using a set of .32 ACP dies. The bullets were cast of WW+2% tin+one cat food can of birdshot to 20 pounds, gaschecked and sized .312, then heat treated. The lube was homebrew. Ready to be loaded, they weigh 159 grains. Book velocity for that load is 2100 fps.
The Barnaul 123 FMF ammo did not do nearly as well as the cast bullet. I'm just getting started and I'll post as I go along, but if the cast load continues to shoot that well, I'll likely stick with it.