normally you can approximate what group size can be had by multiplying your known group size at one yardage say 1"@100yds or meters, would be 1MOA or 1 minute of angle and would = 2"@200, 5"@500 10"@1000, of course factors like wind, bullet weight, twist rate, velocity and consistency affect accuracy and of course how calm your hold is. At longer distences it is necessary to know this and the ballistics for that particular load to adjust your scope properly. if the bullet will drop 6"@400yds when sighted in at 100yds and your scope has 1/4 moa clicks you would adjust them up 6, because at 400 yds 1/4moa=1" and 800yds=2" I always enjoy competing against myself at longer ranges, and if you reload you can make drastic improvement in a relatively short amount of time, I can normally get a dcm ar-15 to group about 4"at 200m with iron sights at my best, but my scoped savage 10fp can do it in 1", but it has taken me about 5 years of constant weekly practice to be able to get to this point