Heym made rifles based on early Yugoslavian Zastava actions in the early 1960's. I know some were imported to the US and sold by Montgomery Ward. All I've seen were based on an intermediate length action that had been modified for 30-06 length cartridges. The trigger guard and floorplate on yours looks identical to what I've seen. What is the distance between guard screws on your action? Also, I don't think the FN commercial actions were C ring.