Winchester took the Model 1866 to 1866 Switzerland Trials in Switzerland.
Here are the results from 300 paces (250 yards) to 1,000 paces (833 yards).
These should be from at some sort of rest position because there is also a 300 pace off-hand target as well.
From Winchester's 1873 Catalog
Over-All Size Of Main Target = 6 feet x 6 feet, 6feet x 10 feet for 1,000 pace target.
Large Squares = 6 Inches
Small Squares = 1/10 of one foot (1 13/64")
I left out the 400 Paces Target
44 Henry Rimfire 300 Paces - 250 Yards Off-Hand
44 Henry Rimfire 300 Paces - 250 Yards
44 Henry Rimfire 600 Paces - 500 Yards
44 Henry Rimfire 800 Paces - 666 Yards
44 Henry Rimfire 1000 Paces - 833 Yards