A survey of the OR for yards, paces and rods has yielded the following firefight ranges (identified opening fire range):
The mean is 95 yards and the mode 100 yards, but three distinct peaks are visible. It seems the average open field range of 100 yards is reasonable, with the lower ranges being in restricted terrain.
During Pickett's charge 2 Union regiments (7th MI and 20th MA) opened fire at 200 yards, the rest at 80-100 yards except the 12th NJ who reserved fire to 20 yards. The attacking Confederates stopped to fire around 80 yards and stopped moving forward well clear of the fence.