During a recent range trip, I decided to try to shoot at an estimated range. The name of the game was simple, walk around for a few minutes and then take a headshot on a far away target of undetermined range.
This game was repeated three times. Once with an ACOG, once with a 3-9x scope, and once with iron sights. Also, shots were taken from a 45-degree angle, not straight-on.
First, I fired a shot using the ACOG. As you can see, the shot was a success.
Next, I put a variable power scope on the rifle. Here is the result of the shot. My forefinger shows the original shot made with the ACOG. My middle finger shows the shot made with the scope. Again, a success!
Finally, I took a shot with iron sights. As you can see, the shop weld up in the neck region. Still, a season-ending injury.
Just eyeballing the distance, I estimated the range to be approximately 100 yards. When I stepped off the distance, it seem to be about 100 yards, as well. When I used a range finder, the result was 102 yards.
The zombie head in this photograph was approximately 3 inches across. An actual human head is approximately 8 inches across. That gives us a factor of 0.375. This gives us a target that appears to be about 270 yards away.
Further corroboration comes from the fact that the zombie body was slightly wider then the ACOG chevron. The ACOG chevron should be the width of a human torso at approximately 300 meters, or 327 yards. A person standing about 50 yards closer would be slightly larger than the chevron.