When you’re zeroing a scoped rifle at short range, save ammo and frustration by paying attention to your turrets. Scope adjustments are measured in angular units, usually MOA or mil. MOA stands for minute of arc or minute of angle, and mil (or mrad) is short for milliradian. An angular measurement covers a greater length as the distance from the measurement point increases. We sometimes see customers struggle to zero a rifle at short range, because they are only adjusting the scope one or two clicks at a time.
A 1/4 MOA turret, for each click, moves the point of impact about 1/4″ (~.26″) at 100 yards. However, at 25 yards each click will move the point of impact only 1/4 of that distance, about 1/16″ (~.065″). So if you are 1 1/2″ off at 25 yards, you’ll need 23 clicks (.065″ x 23 =~ 1.51″) to zero your scope. Some scopes or shooters will round to 1/4″, which comes out to 24 clicks. That’s still close, just remember to confirm zero at the actual distance.
A 0.1 mil turret will move the point of impact 0.36″ per click at 100 yards. In our 25 yard example, each click will still move that point of impact 1/4 as far as if the target were at 100 yards, or 0.09″. If you are off by that same 1.5″ at 25 yards, zeroing your scope will require 17 clicks (0.09″ x 17 = 1.53″.) Again, the .03″ difference is small enough to be insignificant.
There is a lot more to talk about with scopes, zeroing, and adjustments, and this barely scratches the surface. The main point here is that at 20 or 25 yards, you may need to turn the turret more than you first thought. Always fire a 3-5 round group and adjust based on the center of that group. Finally, confirm zero on your gun at the actual distance you intend to shoot at. You may have heard rules of thumb such as “zeroing your point of impact 3/4″ low at 25 yards will hit at 100 yards” or “a 50 yard zero crosses over at 200.” These can save time and get you close to zeroed, but don’t rely on them until you find it to be true with your gun/ammo combination.
Edited 10/11/17 with more accurate math for MOA scale.