How to Choose a Rifle Scope

scopesIt’s time to buy a new scope — but with all the choices in the marketplace, how do you know what’s right for you?

The world of rifle scopes can be a confusing one, especially given the propensity for manufacturers to throw around acronyms, numbers and phrases; some of which were quite literally invented by them and are often little more than marketing jargon. Figuring out what it all means can be a daunting task and figuring out what best suits your needs can be even more challenging. Let’s start with the basics.

Magnification & Zoom

Virtually all optics utilize a numbering system that denotes the magnification first and the objective lens size second. A typical denotation on a rifle scope would be 6×42. The first number indicates the magnification power of the scope and the second is the size of the objective lens in millimetres. A second type of common numbers you’ll see are 3-9×40. In this case, the hyphen indicates the scope has adjustable magnification that ranges from three to nine power and the objective lens is 40mm. Adjustable magnification or variable scopes are the most common style favoured by hunters these days. While early models were plagued with problems, modern variable scopes are extremely durable and hold zero throughout the zoom range. If they have a downside, it’s that they are slightly heavier than fixed power scopes but the versatility they offer over a wide variety of ranges far outweighs the slight weight gain.

One of the biggest innovations these days are scopes with larger zoom ranges. A three-times zoom range has long been the standard, such as with the classic 3-9x but manufacturers are beginning to expand this range. Swarovski brought out their Z6 in 2007 that offered a six times zoom range and Bushnell followed in 2008 with their 6500 Elite that offered an unmatched 6.5 times zoom range. Basically, what this means is that the scope offers 6.5 times as much zoom from its lowest power setting to its highest. Bushnell, for example, offers their 6500 is a 2.5-16x. The price you pay for the large zoom range, however, is a larger tube. Rather than the standard one-inch tube, the Z6 and 6500 sport 30mm tubes to allow for the larger internal mechanics required to achieve the higher zoom range, although Swarovski launched their Z5 in 2009 that offers a five-times zoom range in a standard one-inch tube. Most manufacturers have followed with four-times zoom ranges in their one-inch scopes in the past couple years and I’m sure more will follow suit.

Objective Lenses

While magnification is a fairly simple function of optics to understand, objective lens size is more confusing. The objective lens is the lens at the opposite end of the optic you are looking through, and the size of that lens basically controls how much light reaches the eye and ultimately, how bright the scope appears in lower light conditions. Certainly lens quality and lens coatings play a big factor in the ability of optics to utilize light, but all things being equal, the objective lens determines how much light reaches the eye. A common misconception is that larger objective lenses also equal a larger field of view but it has no bearing on field of view at all. Field of view is a measurement of the amount of real estate you can see at 100 yards and is a function of the internal construction and not objective lens size.

Another misconception is that optics with large objective lenses amplify light. The only optics that truly amplify light are those with built-in electronics, such as night vision optics. The best that standard optics can do is utilize available light and the objective lens size determines how much light can be utilized. As a rule of thumb, the larger the objective lens, the brighter the optics will appear in low light conditions. But, even this comes with conditions. If you divide the objective lens size by the magnification, you get the size of the exit pupil; the amount of light that actually reaches the eye. So, on a 6×42 scope, the exit pupil is 7mm. This is an important number as it gives you an indication of how bright the optics will be in low light but with the proviso that the pupil in the human eye can only dilate to a certain size, restricting the amount of useable light from optics.

For younger folks, their pupils can dilate to a maximum of around 7mm but as we grow older, that size is reduced to 5mm or even lower, so if you are over 30 years old, there isn’t much value to an exit pupil on optics that is greater than 5mm. Large objective lenses are a bit of a trade off. They are bulkier, heavier and require the use of higher rings when mounting, so try to find a combination of magnification and objective lens size that provides a useable-sized exit pupil.

Eye Relief

Eye relief is another factor that should be considered when purchasing a rifle scope. Basically, it refers to where the rifle scope sits relative to the shooter’s eye. It’s the distance your eye is from the scope to achieve a full field of view. On heavy recoiling firearms, having adequate eye relief is important. Each manufacturer typically lists the eye relief for each of their scopes — although be warned that eye relief changes when the zoom setting is adjusted with some brands of scopes. I prefer a scope with a constant 3.5 to four inches of eye relief. While eye relief is measured at a precise distance, most scopes have what’s called non-critical eye relief and you will still get a proper sight picture a half-an-inch on either side of the advertised distance. It’s not as precise a distance as many believe.

Scope Considerations

I’m a big believer that more magnification is better when shooting at ranges in excess of 200 yards. I’m running 4.5-14×44 scopes on most of my rifles these days. I’m also running some sort of a long-range compensation system as well on most rifles. This allows me to shoot at a wide variety of ranges while still holding my crosshairs exactly where I want the bullet to hit. This can be accomplished through the use of external turrets or a ballistic type reticle.

The mil-dot reticle was the first true long-range reticle. Developed by the US military in the late 1970s, the mil dot is still the standard reticle used by snipers today. Through a fairly complex set of calculations, the mil-dot reticle can be used to calculate distance and then the dots can be used to hold on the target through a variety of ranges. The key to long-range accuracy is being able to hold on the target through a variety of ranges and not rely on hold over or as many call it, Kentucky windage. To do this, you require a reticle with multiple aim points or you need to move the elevation turret to match the distance.

Turrets

Scopes with target or externally adjustable turrets have, until recently, been the simplest means of shooting long ranges. Basically, you have a single reticle and you twist the elevation turret to match the range you intend on shooting. This allows you to hold right on the target through a variety of ranges. To set up typical target-type turrets, you’d zero your rifle at 200 yards and then move back to 300 and see how many clicks of the turret it takes to zero it at that range and then you’d move to 400 and so on. Adjustable turrets are an extremely accurate choice for long-range shooting but it takes time to set them up and until recently you had to record the amount of rotation between ranges for reference. You’ll actually see shooters with a table taped right on to the stock of the rifle.

Capitalizing on the popularity of adjustable turret scopes, Swarovski introduced their Ballistic Turret in 2008 with the intention of simplifying the use of these scopes for the average user. Swarovski offers a very comprehensive online calculator that quite literally allows you to set up the scope for shots to 600-plus yards and for a variety of cartridges and loads. Basically, you zero your rifle at 200 and then go to the online calculator and look up your load. There are four coloured markers on the turret that can then be set for increasing ranges. The program tells you exactly how many clicks to rotate the turret for each range you want it set for. If you move the scope to a different rifle or you change your load, the coloured markers are easily moved to compensate.

Leupold and Huskemaw are two other big names in the external turret market. They both offer custom laser etched turrets for your exact load. Rather than having to count clicks, the turret is marked in yardages, so it’s a simple matter of just dialling to the exact yardage before shooting. You can get additional turrets if you change loads or rifles.

Ballistic Reticles

While turrets are popular, it’s ballistic reticles that own the lion’s share of the market. They are typically simpler to use and are much quicker in a hunting situation. Zeiss revolutionized the ballistic reticle market in 2008 with their Rapid Z reticle that is adjustable for a wide variety of loads and cartridges. Their system allows you to go on-line and enter in the ballistics or manufacturer of your load and then receive the info to tune the scope for that individual load.

With the Zeiss reticle, you zero your rifle for 200 yards using the centre crosshair, just as you would with a regular scope. Then, you enter the data for your load and the online calculator will tell you the magnification you need to have your scope set at for the secondary hashmarks. While the secondary hash marks must be used at the specified magnification, the primary crosshair remains zeroed at 200 yards even when the magnification is changed. This makes the scope useable at closer ranges with the magnification dialled down and then you can use the higher, specified magnification for longer range shots. This is the simplest and most accurate multiple reticle system there is.

Selecting the proper scope for your particular application can be a complex task but with a better understanding of optics and what all the buzz words really mean can go a long ways to simplifying things. As with most things in life, you get what you pay for with optics but in an increasingly-competitive market, it’s a great time to be looking for a new scope.

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