I recommend a 50 or 200 yard/meter zero for iron sights (100 for optics).
These are rarely the same thing, despite the commonly spread internet lore. This can be debated ad nauseum, but I have shot a whole lot of rifles at a whole lot of distances and if your accuracy expectation is anything smaller than a full-size IPSC at 200, only a few rifle/ammo combinations will be 50=200.
I prefer a 50 or 200 with irons specifically because the front sight post obscures smaller targets that are being held-over in the critical midrange distances where irons are still useful.
I am a firm 100 yard/meter zero for dots and optics, as that trajectory and line of sight relationship requires less mental horse-power at close range, while providing a more refined POA/POI intersection for longer range drop compensation.