For simple target shooting you can do what is done for CMP shoots (the battle sight zero as descried in the previous link is not used for this).
Crank the sight all the way down. Now crank it up 6 clicks. Shoot at 100 yds and adjust up as need to get as close to the bullseye as you can. Most Garands will be on 100 yd zero in 6-8 clicks up from bottom.
When you shoot at 200 yrds go up 1-2 clicks and you should be close. I think 300 yds is another 3 clicks up. Write down type of ammo and the clicks you needed for each yardage on a piece of paper and store that in the oiler hole in the buttstock. Now anytime you or another person picks up the rifle they can refer to the Click data you wrote down and be pretty close on the first shot for those distances.
"The ultimate authority ... resides in the people alone. ... The advantage of being armed, which the Americans possess over the people of almost every other nation ... forms a barrier against the enterprises of ambition."
- James Madison