Optic shopping can be incredibly confusing. There are all sorts of numbers and specifications and potential features, in addition to the subjective quality of the glass. This can make purchasing a scope that will pair well with a new rifle fairly challenging. Much like your rifle, picking an optic is a function of the intended purpose of the rifle.
Optic Types
First of all, there are several options for hunting optics. The most common type of optic for hunting is a rifle scope. Prism style sights are not usually the best fit for hunting given their fixed magnification, expense, and difficulty mounting to two piece bases. Red dots can have hunting applications but the reduction in precision means that they are best used on rifles meant for speed which have shorter effective ranges due to accuracy and common chamberings. For example, a red dot may be appropriate for a Marlin 336 in 30-30 Winchester, but probably should not be going on a Ruger American in 30-06.
While the red dot is a very fast aiming system, most hunting scenarios favour the precision offered by a scope. Scopes can either have a variable magnification (zoom) or fixed magnification. Usually, fixed magnification scopes are a little clearer that variable power scopes of the same price range. On the flip side, variable power scopes offer greater flexibility for a wide range of hunting scenarios.
Desirable Attributes
There are a few desirable attributes in a hunting scope. These attributes are what contributes to the various price ranges in scopes, and are what separates a one-hundred-dollar scope from a one-thousand-dollar scope. By spending more money, you will get a scope that does the following things better.
The first of these attributes is an ability to hold zero. Very cheap scopes will struggle to hold zero under impact. These impacts can come from the bumps and jostles that occur from carrying your rifle through the woods. Nothing is worse than knocking your rifle off zero while miles into the backcountry, potentially ending your entire hunt. Alternatively, these impacts can also come from the recoil of the rifle. Large magnum rifles are much harder on scopes than rimfire plinkers. As such, it is a bad idea to put a cheap scope on your 338 Winchester Magnum and expect it to hold zero. Fortunately, the ability to hold zero well is quite reliable for modern scopes once you get above around the two-hundred-dollar price range.
The next attribute is the ability to track properly. Most scopes will have ¼ MOA adjustments, which means that for each click the point of impact should shift by roughly a quarter inch at 100 yards. This scales to a shift of a half inch shift at 200 yards, all the way out to 2.5 inches at 1000 yards. A scope that tracks well will move consistently and correctly every time, and will return to its original setting precisely. This is very useful when sighting in, as well as making elevation adjustments for longer shots in the field.
Lastly, the final attribute is glass clarity. More expensive glass is clearer, with less distortion. This translates to more accurately identifying your target as well as increased performance in low light. Because deer are more active at dawn and dusk the ability to see well in first shooting light is very desirable. A lot of what you pay for in a two-thousand-dollar scope is top notch clarity in the quality of the glass.
Magnification
Next, you need to pick the right magnification range for your application. Most novice shooters believe that higher magnification is better, and if the goal is to shoot small groups at the range they are probably right. However, a veteran hunter knows that as the magnification increases, the field of view decreases. That means that finding your target in the scope at 24 power is much harder than it is at 3 power.
An old friend of mine once chased a wounded bear into a patch of blueberry bushes. Imagine his surprise when he jumped the bear at 5 yards only to discover he had left his scope at 9 power. When he looked through the optic, all he could see was black. Luckily, his shot found the bears vitals and nobody was hurt. However, it certainly taught him a lesson he has never forgotten. To this day he compulsively checks his scope in the field to ensure it is always on 3 power.
Personally, I find that a low end of around three power with a top end of 16 power or less is a good range for most hunting applications. Three power is adequate for close shots, and one rarely goes above 10 power in the field, even for longer shots. The classic 3-9 range is no longer cutting edge, but there is a reason it is so popular.
Objective Lense
Next, you need to select the size of the objective lense. Larger objective lenses gather more light, which leads to better low light performance. On the other hand, larger objectives make for heavier optics. I prefer an objective lense in the 40-44mm range in order to keep my optics light. This compromise is acceptable, because I locate game with my binoculars, and my rifle scope is only an aiming system.
Reticle
The final aspect that should be considered is the reticle. Many deer have fallen to the classic duplex crosshairs, and it works well out to around 300 yards or so. More complex bullet drop reticles can be helpful for longer shots, but ensure you test them at the range before taking them out hunting. Oftentimes the reticle doesn’t perfectly line up to your cartridge, barrel length, and loading. As such, testing is needed to know exactly where your rifle shoots. Also, be wary overly complex reticles. They can be difficult to focus on in sub-optimal conditions like low light or brambled shots. In the heat of the moment, it is important to remove as many potential sources of human error as possible.
Concluding Thoughts
In conclusion, rifle scopes come in many shapes and sizes. For most hunting scenarios, simpler is better. Spend enough to get an optic that holds zero and tracks reliably. Pick a scope with a modest magnification range and a relatively simple reticle and you are prepared for 90 percent of hunting scenarios. As long as you follow these guidelines, your optic won’t be the reason you lost the buck of a lifetime.