Read the Spot and Stalk part of the Big Game Hunting section first, then continue with this section.
The longer the range, the higher the desired magnification. When it comes to magnification, however, less is more. That’s because of the effect of higher magnification scopes have higher veiling glare. Higher magnification scopes also require larger objectives for the same brightness. The larger the objective, the more glare. Finally, veiling glare increases significantly outside of the exit pupil. If the eye pupil is larger than the exit pupil, the eye will collect more of this glare. That’s in addition to the decrease in brightness when the eye pupil is larger than the exit pupil. Therefore, increasing both the magnification range and the objective size has a compound effect on increasing glare. The effect can be particularly dramatic for small exit pupil sizes. The bottom line is: buy only as much magnification as you really need, and no more.
This advice is contrary to popular practice, in which long range hunters often buy >20X rifle scopes. The main argument for this seems to be “so I’ll have it if I need it.” Such a high magnification is usually unnecessary and comes at a cost.
In terms of target angles, the size of a typical reticle line is roughly 0.1 MOA, and the size of a reticle dot is 0.125 MOA (fine target dot) to 0.9 MOA (USMC mildot). The vital zone diameter is about 8 inches on most big game. At a range of 1,000 yds, an 8 inch diameter subtends 0.80 MOA. At 15X magnification, the vital zone is magnified to 12 MOA.
This means that the shooter must position the reticle crosshair or dot on a 12 MOA aim point. Recall that the eye has a resolution of about 1 MOA. The angular dimensions of the vital zone is ten times the resolution limit of the eye. The animal’s chest is at about 24” tall, which equals about 36 MOA at 15X magnification, or 36 times the resolution of the eye. This aiming task is fairly easy for an experienced shooter to perform.
Increasing the magnification from 15X to 24X makes the entire sight picture appear 60% larger, but doesn’t make the aiming challenge fundamentally easier. Increasing the upper magnification limit from 15X to 24X, however, significantly increases glare at all magnification settings. For a 50 mm objective, the exit pupil decreases from 3.3 mm to 2.1 mm, reducing both image brightness and eyebox size, and increasing glare for larger eye pupils.
Veiling glare can be reduced for high magnification scopes by the use of a sunshade. While a sunshade can obstruct the field of view for a low magnification scope, it has little or no such effect on a high magnification scope. In general, if you can use a sunshade, then do so.
One exception to the “less is more” rule for magnification is when the hunter has vision problems. Near- and far-sightedness can be corrected using the diopter adjustment on the ocular. Astigmatism, however, can only be corrected using glasses and contact lenses. Shooting without this correction will cause the image to blur. Having a higher magnification will make the blur less of a problem. The best approach is to hunt with vision correction, if at all possible. Doing so will also improve image clarity using a binocular and spotting scope. If the astigmatism is mild and the hunter otherwise has adequate vision at long distance, then a modest increase in magnification is a viable compromise.
Read the section on Elevation Adjustment at the end of these quick guides.
First consider scopes with good glare performance and good correction of off-axis aberrations. An upper magnification of 20X or less is recommended. Then select the rings and base, which determine the elevation adjustment requirement. That is, 90 MOA for standard rings and base, vs 50 MOA for a properly selected and installed biased base (i.e., 20 MOA) or Burris Signature rings using either a dovetail or Weaver base). The use of standard rings will significantly restrict the number of scopes from which to select.
Then select the reticle, turrets and other features from the remaining group of scopes. At ranges of up to about 500 yds, ballistic drop corrected (BDC) reticles can be accurate if calibrated and zeroed properly for altitude. BDC reticles with windage hold-off marks or dots are effective, but introduce more clutter into the sight picture. We recommend BDC reticles in the SFP location, because it then the zoom ring can be used to calibrate the scope to the ballistic drop profile of your caliber.
The greater precision of a calibrated BDC turret is necessary for ranges >500 yds. At ranges of up to about 750 yds, ballistic drop corrected turrets can be accurate if calibrated and zeroed properly for that altitude, and atmospheric conditions (barometric pressure and temperature) are similar to those when the calibration and zeroing were done. Variations of more than +/-1,000 ft or +/-20 °F can cause enough aimpoint error to miss a shot at >700 yds. Multiple custom turrets are therefore needed if you hunt in widely varying altitudes and temperatures. Beyond about 750 yds, even daily variations in temperature and pressure can cause significant aiming errors. Reticles with horizontal subtensions that enable holding for wind are particularly useful when using BDC turrets. Plex-type reticles can also be used with specialized windage turrets that dial +/- hold-off values from a resettable zero.
Of course, graduated reticles (mildot, etc.) work very well at ranges >750 yds when used with range cards or a ballistic computer. Mildot-type reticles have a somewhat standardized format and allow range estimation. Once learned, they can be very accurate at long range.
All of these reticle and turret options benefit from a good ballistic computer. Ballistic computers enable you to select calibers and bullets, calibrate your BDC reticle to your caliber and load, and generate a custom range card for every hunting location. The wide variety of accurate ballistic smart phone apps now makes portable ballistic computers affordable for nearly everyone.
Scopes are commonly found with mildot reticles and MOA turret adjustments (called “mil/MOA” scopes). The availability of scopes in either mil/mil or MOA/MOA formats is improving, but these scopes often carry a price premium. If you are just starting out using a mildot-type reticle, it doesn’t matter much whether you have a mil/MOA, mil/IPHY, mil/mil, or MOA/MOA scope. Most ballistic computers will provide elevation and windage hold-off values in any of these units. For example, you can dial the elevation in MOA and hold-off windage in mils. It really doesn’t matter that the units are different. You only care that the ballistic computer outputs the units that your scope uses.
For both BDC turrets and mildot-type reticles, accuracy of reticle movement is an important mechanical performance requirement. In addition, the vertical reticle adjustment must be large enough for your caliber and range (this topic is discussed in more detail below).
A standard eye relief of 3”-3.5” is fine for lower recoiling calibers up to 30-06. Heavier recoil calibers may require longer eye relief. Training yourself to hold the rifle firmly against your shoulder is advised.
With very few exceptions, scopes with good optical performance are likely to cost $400+ MAP. The latest turret and reticle designs, better durability, more accurate reticle adjustments, and lower glare will justify substantially higher prices.