When I was researching a while ago, the prevailing opinion was that you should 1/2 the manufacturer's claim.
Thus a 1000m unit was good for about 500 in real world conditions.
That advice turned out right for me and the model xxx600 that I ended up buying.
And to be honest, I've never taken it stalking.
I take it when I go for a walk, just to practice, verify, my visual estimated range to a tree, or a gate, whatever.
Now I am reasonably good at establishing range.
M