Althought not completely universal the 100 yard zero is very common. From a 100 yard zero setting we can all talk about the number of Minutes of Angle (MOA) we need to get to a certain distance and hold for Point Of Aim (POA) to Point Of Impact (POI). As an example: I use a 308 Winchester a lot so when someone asks me for my 500 yard data for a particular load I simply reply "11.5 Minutes Up" which they immediately (in most cases) understand to mean that I adjust my scope up by 11.5 MOA over my 100 yard zero. Many of the long range shooters have a little chart taped to their rifle somewhere. This little chart shows distances and elevation numbers. (My chart is inside the rear scope cap) I can loan my rifle (AND ammo) to another shooter and after he verifies that his 100 yard zero while shooting my rifle is correct for him he has all the additional data he needs to shoot the rifle to any distance (1000 yards or so).