The Krieghoff I used to have liked the following load.

570gr Woodliegh
Jamison Brass
CCI LRM primer
105gr IMR 4350

Make sure you have a good crimp on each round. I used to clamp a padded bracket to one of the roof posts at my range, this gave me a steadying rest for the back of my left hand, I would shoot standing offhand this way to keep the recoil correct and to get some added sight stability.

Did you buy the Heym new? Another option is to have them sort it out.