I thought this would be a good place for this. I currently have a Bushnell 400 rangefinder. For field trials it isn't enough, it's fine under 100 yards. I can put the little square on a person with a white coat on at ~200 yards and it will seldom give me the range. I have tried out the same thing but a Bushnel 600 unit and it wasn't any better.
What will work to find the range of a gunner out to ~400 yards?