Laws of Physics always apply....
The amount any given bullet falls in a fixed time period is related to the pull of gravity. Nothing will ever alter that.
A bullet that moves relatively fast will have less time to fall at 100 yards than a slower moving bullet. Once the velocity of the bullet is known, calculating the drop at any given distance is just a matter of running the formula. The only real problem is that factory ammo claiming to produce X fps of muzzle velocity, may be faster or slower in this particular rifle.
Someone brought up the difference between iron sights and scopes. The only difference is the scope has (usually) a greater distance between 'line of sight' and 'line of departure'; which is to say, the line of sight through a scope is higher above the boreline, usually. This is not true if one compares a scoped model 700 in .223 Remington and an AR15 variant. The sights on AR15 type rifles are pretty high in comparison to a bolt gun.
However, in sighting in a rifle, a lot of the mathmatical calculations can be deleted. Simply sighting in at 25 yards will put the bullet strikes 'on paper' at 100 yards. For most centerfires with a muzzle velocity above 2500 fps, it's probably on paper at 200 yards as well.
And yes, it also works for windage. However, remember values for 'clicks' vary with the distance. One 'click', either iron sight or scope, will move the bullet strike four times as much at 100 yards as it does at 25 yards. To put it another way, if your bullet strike is one inch 'out' at 25 yards, it will be 'out' the same direction, but four inches 'out' at 100 yards.
Someone mentioned 'battlesight zero'. The idea here is to get as much range without changing sights as possible. The concept works very well for hunting rifles.
Take a look at the attached chart for the information on the .30-30 rifle: it shows a 25 yard 'spot on' impact, 2.75" high at 100 yards, 2.25" high at 150 yards, .25" low at 200 yards and 5 inches low at 250 yards. So if your .30-30 rifle is sighted in as shown, you can use the same sight picture, not hold high or low, and get bullet impacts out to 250 yards that are never more than five inches from your point of aim.
This is presuming you are using 150 grain bullets and they actually develop the velocity, not shown here, as used to calculate this chart, your rifle will shoot this tightly and you can hold that well.
Mustanger, when I was in the Marine Corps, the 1,000 inch range was used as a sighting in mechanism only. By the way, 1,000 inches divided by 12 is 83.33 feet, divided by 3 is 27.77 yards. It was designed to be perfectly compatable for zeroing the military ball ammo loads for both Garand and M14 rifles. Turns out it's close enough for M16 rifles as well.
The long and the short of it for sighting in is this: Getting on paper at 25 yards beats the heck out of wasting the first six or eight shots (out of your box of twenty) trying to figure out where your shots are going off the paper at 100 with your brother in law telling you "Yer tooo fut ovv 'n da'dirt t'da rate!"
