In pre-M16 days, when we used the M-14 we used the Canadian Bull to get a battle sight zero. Aim at the bull (black) and the impact for ball was the bottom X (top X for 5.56 M193). This is a 1000 inch target that gave you a zero of 250 meters.
On the M1/M14 sights once you got it zeroed at any range, You set the dial for that range and you were good to 1200 yards by using the respective mark. You had a number for even yardage (2-200, 4-400 yds, etc.) and a hash for odd number yardage (1-100, & a "-" between the 2 & 4 mark for 300, etc etc) Best sights ever put on a battle rifle.
As Greg indicated, your come ups are: For 1 min clicks:
100-200 2 clicks
200-300 3 clicks
300-400 4 clicks
400-500 4 clicks
500-600 4 clicks
600-700 5 clicks
700-800 6 clicks
800-900 6 clicks
900-1000 7 clicks
1000-1100 7 clicks
1100-1200 8 clicks
This was for Ball ammo, but in reality there isn't that much difference in the ammo the military used.
For example the Angle of departure for the '06, is 2.7 for M1 ball, 2.3 for M2 ball, and 2.4 for M2 Armor Piercing, Moving to 1000 yards the angle of departure for M1 ball is 43.5, 44.6 for M2 ball ad 46.2 for M2 Armor piercing.
That's the quit and dirty, however nothing beats getting a zero for each yard like you expect to shoot. But for combat the above worked quite well.
The witness marks are the M1/M14, again are the best sights ever put on a military rifle. Back in the day where I was running sniper schools different companies would show up at the guard trying to sell scopes. My state (Alaska) was big on sniping so the powers to be would have me test these scopes. Back then they didn't have the stuff they got now, but for example , Shepard Scopes guys had what the considered the cat's meow on scopes. There range estimations wasn't near as good as the iron sights on my M1, meaning when I set the witness mark at a given range the impact hit that range, Not so for the Shepard that was suppose to be calibrated for the same ammo.
As a side not, the 50 yard increments on the M84 scope used on the M1C/Ds were the say way. You set them on a certain yard mark the rifle hit at that distance.
But I'm not in the game any more, and I sure as hell am not going in combat, so I have sight settings for every yard line I shoot, 100, 200, 300, 600, and 1000.
