I've heard that you can sight in a rifle with scope at 25 yards and the settings will be the same at 100 yards. For instance if sighted in 1 inch high at 25 yards it will also be 1 inch high at 100 yards. Is this true? :confused:

Reason for my asking is that I'm having a little trouble being able to get to a 100 yard range, but have easy access to a 25 yard range that will handle rifle fire. Thanks for your time.

25 yards should get you on paper at a hundred, but won't be a a guarantee of exact placement at a hundred. Different sight hights effect where it will shoot along with different cartridge's.

Your still going to have to shoot your rifle at the ranges you expect to take game at, otherwise your just guessing where that bullet will go.

Out here in the West where we can shoot some long ranges my 280 Remington, for example is sighted in three inches high at a hundred.

considering a sight plane 1.5 inches above the bore, and generally speaking, most high powered rifles will be about .5 inches low at 25 yards for a 100 yd. zero. the problem with this is that for every fraction of an inch error at 25 yds. will increase by a factor of four at 100 yds, factor of eight 200 yds, you get the idea. my experience is bullets of varying construction tend to flight differently at ranges over 50 yds. so what bob said about shooting at ranges you expect to take game is spot on.

Please correct me if I'm wrong. The run of the mill .270/.308/.30-06 will theoretically land again at 200 yards at the elevation it hit at 25 yards. At 100 yards, it will (again theoretically) be 2 1/2" or so inches high. But more importantly, do what Bob and Richard have recommended. You will see in my thread from a couple days ago about sighting in my new Bushnell scope that I stopped at 50 yards. I do from time to time get shots at game over 50 yards away. I have shot my rifle/load combination alot at 100 yards, hence my stopping at 50. I know from previous experience what that bullet is going to do from 50 to 100 - rise up, & spread out a little, but still be deadly accurate. Figured I'd save the ammo. If I'm ever fortunate enough to participate in a western states hunt, I will surely be practising long range.

A lot of theoretical there. It might work, or it might not.
I use the 25 yard to the rifle close to the point of aim before I shoot at longer distances.
What you could do, after you sight in at the longer range, is to see where it shoots at 25 yards. That could be useful if you have to do a quick check to confirm sighting (bumped the rifle, dropped it, etc).

Jack O Connor wrote a story about the 25 yard sight in years ago and it will get you close to where you want to be at 100. I always sight at 25 and move to 100 and work from there. What Richard said is true any bit you are will magnified x4 at 100.